Daniel.. I'm so sorry.
Nothing quite crushes your soul like rejection, but here you are blaming yourself! WHY!!
This woman chose to spend her days and nights thinking about another man while lying with you. It has nothing to do with religion. It's loyalty, and it's something she doesn't have. And to then tell you about it, how cruel.
My feeling is that there is not a single thing you can do about it on your own. in the best of circumstances it will take love, commitment, dedication and WORK from both of you, and it appears only one of you is prepared to put those in. She is blaming the fact you stopped going to meetings, but I think it's a lot deeper than that..
Hugs to you, If I could pray.. I would, but I think time and self belief are the tools you need to put this behind you.
Poppy