Don't think in terms of where you want her to end up. Work out where she is now, and present a position one inferential step away from her current position.

In my Intro To Logic class that I took a long time ago, the teacher led the class in a deduction about evolution. You could basically lead her through the deduction and invite her to poke at the premises, yourself, if you are confident enough talking about it. You could even sketch it out on a napkin in a restaurant. If my outline is insufficient, just let me know what I can do to help you flesh it out to your satisfaction.

1) Scarcity - there aren't enough resources for everybody to get all of what they need/want. (In my experience, some Christians deny this, claiming god will provide. You could easily counter that if that were the case, there'd be no such thing as economics. Or point out that there's half a million people starving to death in Botswana who might disagree).

2) Variability - There's differences between individuals in a population (I haven't had any trouble with getting people to agree to this one).

3) Inheritance - Differences between individuals can be passed down to descendants (They might need a prod by saying that kids grow up to look like their parents, or something like that).

4) Because variability can be passed down to future generations (via 2 and 3), any variability that makes you better at getting a bigger slice of scarce resources gives you a better chance to have babies.

I know it isn't technically a deduction, since I didn't introduce every term and show how P1 & P2 => C1, etc, but I imagine formal logic isn't something your friend cares much about.

A biologist friend of mine has had limited success with this method. He has also suggested that the book "Why Evolution Is True" be read by novices who are open to actual dialogue but don't know enough to accept evolution.

There is another effective framing technique that I almost never see used that might be worth considering because I've seen it used well in the past.

Most people think evolution is a purely biological concept and it is virtually always framed in such ways. This runs headlong into the mystical beliefs many people attach to living organisms. Making evolution a property of an organism is no different than making a "soul" the property of an organism to them, and fits in the same cognitive pigeonhole. A lot of the jumbled chemistry and thermodynamic arguments follow from this as well; biology is special precisely because it can violate the laws of science.

Evolution is fundamentally a systems dynamic from mathematics. If you have a system -- any system -- with a certain set of abstract properties then there are certain required mathematical consequences. The result of 2+2 is always 4, no matter where in nature we find it. Biology is just one type of system to which this mathematics is applied; it has the prerequisite properties on the left hand side of the equation that require the system dynamic biologists call "evolution" on the right side of the equation. Mathematics asserts that evolution should exist in biology whether or not science has found evidence of it (fortunately, we have found much evidence). When evolution emerges from mathematics instead of biology, it has a sterilizing effect on the concept.

It turns out that very few creationists are willing to dismiss mathematics in the same way they dismiss science. Mathematics is neutral territory, it does not have a political or religious affiliation in the minds of most people, and almost everyone tacitly "believes" in it because they use it every day. The few times I have seen this strategy used -- completely divorcing evolution from science -- even the militant true believers found themselves at a loss for a counter-argument (not that it changed their minds).

The easies thing to do would be to give her a copy of TalkOrigins' Introduction to Evolutionary Biology. It's excellent, and not too long. It may overwhelm her, though, so if you'd like to write something of your own, I'll give some suggestions. I used to argue with creationists as a hobby, so this is kind of nostalgic for me.

What kind of creationist are we dealing with here? Is she a young-earth creationist who thinks the world is a few thousand years old, or an old-earth creationist who won't choke on basic geology? If she's an old-earth creationist, I would suggest reading up on a few fun geological processes that took longer than she thinks the earth has existed. One thing in particular to mention is how we do radiometric dating; a lot of creationists have this silly notion that we try to carbon date everything, no matter what the time-span, and that there's no corroborating evidence for any of it. With few exceptions, these people have never heard of things like potassium-argon dating or the geomagnetic polarity reversals that mark time on the sea floor. Or dendrochron calibration, or the passing of the seasons recorded in ice sheets. If your friend is a young-earther, infodumping about this stuff in a basic way should be moderately upsetting to her, in a good way.

General advice that applies to all kinds of creationists: if you're not going to be arguing back-and-forth with her, then you should try to make her feel doubt. For example, you could quote the head of the Human Genome Project, Francis Collins:

As someone who's had the privilege of leading the human genome project, I've had the opportunity to study our own DNA instruction book at a level of detail that was never really possible before.

It's also now been possible to compare our DNA with that of many other species. The evidence supporting the idea that all living things are descended from a common ancestor is truly overwhelming.

I would not necessarily wish that to be so, as a Bible-believing Christian. But it is so. It does not serve faith well to try to deny that.

But I have no difficulty putting that together with what I believe as a Christian because I believe that God had a plan to create creatures with whom he could have fellowship, in whom he could inspire [the] moral law, in whom he could infuse the soul, and who he would give free will as a gift for us to make decisions about our own behavior, a gift which we oftentimes utilize to do the wrong thing.

I believe God used the mechanism of evolution to achieve that goal. And while that may seem to us who are limited by this axis of time as a very long, drawn-out process, it wasn't long and drawn-out to God. And it wasn't random to God. [He] had the plan all along of how that would turn out. There was no ambiguity about that.

There are compelling arguments you could make against the idea of an intelligent designer shaping evolution -- the design mistakes, the existence of horrific parasites, the breathtaking cruelty of certain parts of nature -- but it would be a victory if you could just get this friend to admit that evolution happened at all, God-guided or otherwise.

Give her a glimpse of the mountain of evidence that she's denying. Talk about fossils, and mention the standard rebuttal to the "no transitional fossils" nonsense. Touch briefly on modern phylogenetics, reconstructing the tree of life by looking at patterns in the genes of living animals. Find some specific examples of coevolution between species, and exposit. Richard Dawkins' books tend to be excellent sources of detailed examples, presented with his usual cheerful enthusiasm; I recommend them.

TalkOrigins is a treasure trove. Some especially useful pages are their FAQ listing observed speciation events, and the list of crappy designs in nature. Also useful is creationtheory.org, which is more focused than TalkOrigins and an excellent resource. You might also try explaining why evolution does not violate the laws of probability, which is a very common creationist argument.

Good luck planting a seed of doubt. That's all you can realistically hope to do right now, so don't get discouraged if she doesn't change her mind right away.

I was at her house tonight. I asked a few probing questions to get a framework of what I'd say:

1) How old do you believe the earth is (her answer was something like a few million, which seemed pretty arbitrary to me but which was apparently based off of a particular argument she'd read)

2) Do you believe in microevolution? (the answer is yes, but not because of knowledge of evolution - it's because of the practicality of fitting all the animals onto the ark. Two of each "platonic" animal that then evolved into similar things)

3) What exactly do you want to know? (the answer was "enough background knowledge so that when she goes to argue with her friend she'll know what she's talking about." But she also was genuinely interested in having some conversations with me about it, just to get a better understanding of what I believe and why)

4) Could you think of any circumstances that might change your position on macroevolution?

The answer was no.

After a quiet mental facepalm, I steered the conversation towards the ability to change our minds and hard but necessary an ability it is. I don't think this was necessarily optimal, but past experience has taught me that when I hear a creationist make that kind of statement, I know that the discussion is already over - anything else we say is just for fun. Her answer was consistent an unapologetic: "The only way to change what I believe is to prove that Jesus wasn't the son of God."

A lot of people recommended simply stating the facts. I think you really grossly underestimate how much bias at work here and how non-obvious your interpretations are to someone with no scientific training. We didn't have internet so I wasn't able to grab a reference to transitional fossils. I'll be linking her to Talk Origins. (Rereading it, I was almost surprised at how good a reference it was. I had forgotten. But it's a little intimidating to just throw at someone).

We did have a good long conversation, which I considered somewhat productive. It ended up focusing more on the Bible than on evolution. She seemed less confident towards the end. (She kept saying stuff like "Josephus is an independent historian who mentions Jesus" and I said "yeah but his testimony came 100 years later and basically carries no wait" and she said "no.... lemme look it up... oh... huh"). Past experiences suggest that these temporary lapses in confidence will be repaired within a few days.

Eventually the conversation turned back towards evolution, and I ended with the "math and genetics" angle, but by then she was tired and I think I wasted the moment.

I still feel like there needs to be a Pro-Evolution book that very carefully unpackages it in a way that doesn't automatically set off a creationist's memetic immune system. (I'll check out Why Evolution is True and see if it comes close). I actually think I'm pretty good at that, but I'm not a biologist and I don't care enough to do all the research necessary to write an all encompassing book.

Explain a bit of how genetics works, then mutation, then heredity, then selection, then show how the combination causes evolution.

This is a lesson from my 10th grade biology class:

Take a bunch of marbles with two different colors. (Lets say blue and white)

Explain that these are the possible alleles in the population, with blue coding for hair and white failing to code for hair.

If a rabbit inherits any blue marbles, it has hair. If it has only white marbles, it isn't born with hair. White marbles represent recessive alleles, but that's not particularly important to evolution.

Now mix all the marbles up in a bag/hat/whatever and draw them two at a time. This produces one rabbit. Write down what that rabbit's traits are. The mixing and drawing represents random mating, saying that all the living rabbits have 2 children, with randomly selected other rabbits. These assumptions aren't accurate, but evolution will still be demonstrated when...

You draw out all the marbles and produce a generation of rabbits. Now say that the winter was really cold and killed all the hairless rabbits. Remove all the pairs of marbles which are all white.

Mix marbles, repeat, take note. Explain that the white alleles are being selected out of the population.

Now just say that surviving rabbits will consume resources to make up for the deaths of the white ones, or not. This basically just demonstrates that a selection pressure will remove deleterious genes from the population.

It will still probably take work to explain that mutations will lead to different traits which are then selected for.

1. Give her a line of retreat by proposing that evolution is compatible with the Original Sin interpretation of genesis (which is very important to her and I would never attempt to argue against).

I can see why this is useful as a rhetorical trick but I don't see how you can argue for compatibility without twisting evolution. All of the core elements, both historical and metaphorical, of the story of Original Sin run counter to actual fact.

beriukay's post below seems like a good place to start. I might stress that evolution is inherently a bottom-up phenomenon: there are a few guiding principles that make sense, and if you accept the principles in one region then they can apply in every region and explain everything. Once you buy that microevolution can happen with moths and wing colors, and understand the two forces of mutation and natural selection, then you have to buy that macroevolution can happen. If wing color can be changed by mutation, then why not embryology?

http://lesswrong.com/lw/kr/an_alien_god/

There are a few demos which use genetic algorithms to demonstrate various evolutions.

A few caveats with each of them, but the basic selection effect is conveyed.