My gut instinct is to find ways to get her to think about other religions instead. If she's basing her belief on an emotional feeling and needs an anchor, you might be able to point out that there are other religions which have more general anchors, instead of extremely specific ones. I could see the discussion going along the lines of "which is more likely, a major earthquake happening in california, or a major earthquake happening in california that strikes los angeles?", eg "which is more likely, the existence of a god, or the existence of a god that also happens to be made in the image of man?"

Regardless, the more general her anchors are, the easier it will be for her to give them up, or convert them into something more correct. I've seen people go from "some arbitrary god is out there" to "god is the universe" to "there is no god" pretty easily, but to shed the shackles of "I believe in our lord and saviour jesus christ who died for our sins" is much harder, if only because it's so much more specific and detailed.