This is going to be long and take what I say with a grain of salt if you wish, but I am in the exact opposite position of you and your fiance. I am the Catholic, and my husband is Lutheran. Both of us were raised in our respective religions, and we are both devout practicers of our faith raised by wonderfully religious parents.
However, we discussed this WAY before we were even engaged. After we had been together for about a year and a half, and I think we realized marriage was probably in our future, we sat down over the course of a few months, and we really hashed out a lot of our opinions on faith, family, raising kids, birth control, Church, etc.
I was very clear that I could not and would not marry him if he could not promise in good conscience to raise our children Catholic. He agreed with me then, he agreed with me in pre-caana, he agreed with me at our wedding, and he still agrees with me today.
That isn’t to say that there weren’t rough times back then when we were hashing it all out. His parents [especially his mom] are very vocal about how unhappy they are that we will raise our children Catholic. They got over me being Catholic, but the kids…well…that’s another story. He wasn’t sure he could deal with his kids thinking he wouldn’t go to heaven, because he wasn’t a Catholic. We hashed that out with a priest.
This should have been addressed eons before now. Are you getting married in a Catholic Church? You have no choice but to raise your kids Catholic. That is addressed in pre-caana and again in your vows.
The husband is the spiritual head of the household. My husband prayed about it during our dating period, and it came to him that as the spiritual head it was his job to ensure the children were raised Catholic. He feels that while he may not be Catholic, it isn’t about him. It is about his family.
My husband won’t convert either. He does not agree with some of the fundamentals [ie. the relationship Catholics have with Mary, the existence of a Pope, etc], but he attends Church with me most Sundays. He attends Lutheran service on Saturday evenings. I attend Lutheran service with him about once a month, but I always go to Catholic Church on Sunday. He volunteers at the Sunday School where I teach as an “arts and activities helper.” He coaches the CYO football team. He makes a conscience effort to educate himself in the practices of the Catholic Church so he can provide his children with information and be a good role model to his CATHOLIC children. He will continue to attend Church with me and the kids [should we be blessed with any] and just not receive Communion.
You need to hash this out NOW. Call a priest, explain what is going on, and start praying. I hate to say it, but I think that this can be a dealbreaker for a lot of people.
However did you never talk about it prior to now or did you think you would get her to change? If that is the case you were very naive…religion isn’t something people give up very easily.