Like mature adults? You seem to be assuming she doesn't have her reasons. As long as she isn't forcing it down my throat and it doesn't interfere with our daily lives, I don't give a shit if she believes in god. If it makes her happy, that makes me happy.
Even if the open windows of science at first make us shiver after the cozy indoor warmth of traditional humanizing myths, in the end the fresh air brings vigor, and the great spaces have a splendor of their own - Bertrand Russell