Why, really, do nerds wear glasses?
If after all these suggestions you're thinking "в But I really like her. If we have children, they will be OK to go to your church, but not compelled to do so, and never baptized.
We need to believe fully and then we make choices, not the other way around. And of course, when it happens, no one the leaver or the faithful spouse could have predicted it.
It MAY be true that she will be miserable with him and make him miserable with her.