Steve,
I think I echo the sentiments of some here. Don't be too "against" her former faith....because you may end up pushing her to it. At the same time, you really need to learn about the religion. It is VERY likely that especially after having a child, at the time parents seem to think about what direction they want their family to go and so forth, that she will consider going back.
Are her family active JW's?
If you love her you love her. If she loves you, then you both should be able to have an adult honest conversation about this.