Unfortunately, this is what generally happens. It can start a few months after baptism or a couple of years but the enthusiasm and joy or your new found beliefs start to crumble. Its because its all a facade !!
At first all you can think about is the new system and living forever in paradise, then you realize pretty quick what you have to pay to get it................yes, the dreaded FS. As she is in a divided home it is soooooooooooo difficult. All you can do is ask her if shes happy being a JW and if not why not ??? She wont admit it to you but she may start to admit it to herself.
I feel so sorry for her (and you) but I know what shes going through. Her drive is most properly saving the kids from the big A and getting you in the org.