As to how to navigate this: suppose that she has a psychological need to profess a belief in some sort of deity, such that she could not fully thrive without professing that belief. Would you want her to be an atheist then? How can you tell if she has that need or not?

"How can you tell if she has that need?" is a little silly - you do what humans do all the time and make your best guess, mostly based on what humans are like on average. Being careful, of course, not to privilege the hypothesis just because it's in the rhetorical question.