Wait, couldn't people have been programmed by evolution to grieve no matter what they truly believe about where the deceased went?

This I can understand.

I am a protestant Christian and your friend's experience with "belief" are similar to mine. Or seem to be, from what I gather in your post.

One thing I've come to realize that helps to explain the disparity I feel when I talk with most other Christians is the fact that somewhere along the way my world-view took a major shift away from blind faith and landed somewhere in the vicinity of Orwellian double-think.

The double-think comes into play when you're faced with non-axiomatic concepts such as morality. I believe that there is a God - and that He has instilled a sense of right and wrong in us by which we are able to evaluate the world around us. I also believe a sense of morality has been evolutionarily programmed into us - a sense of morality that is most likely a result of the formation of meta-political coalitions in Bonobo communities a very, very long time ago.

These two beliefs are not contradictory, but the complexity lies in reconciling the two. This post is not about the details of my Escher-esque brain, so suffice to say there are questions unanswered by viewing only the scientific side and there are just as many unanswered if viewed only from the spiritual side.

Simply because your friend is not blind to contradictions in the Orthodox Jewish belief system does not mean she does not sincerely believe - or that she's deceived herself into believing that she believes. It means that she, as all intelligent believers who practice crisis of faith should, understands just how much she doesn't understand.