" . . . and stirred up a sense of outrage at the assumption that I needed a higher power to validate my gender identity. "
Really? Is her ego so fragile that this is how she interprets such a gesture? I don't need anyone to validate my gender identity, and that's not what this was about. It was about support, not validation.
Whether she values the well-meant show of support from an ally with religious beliefs or not is her business. I don't much care what people believe as long as it doesn't hurt others. But is she really in any position to discount support from any ally? Or is she just being crass?
Apparently she hasn't considered herself atheist for very long. Whatever happened to "No, thanks, I'm an atheist." and just moving on?