Honestly, I don't have very good advice, but keep being you and hopefully she won't let her religion blind her like it blinded me. I'll keep being me and we'll see what happens.
Again, I deeply love my dad, but these were things that I had to deal with.
I also think that if marriage outside the covenant is a sin, it is not so grave as to be unforgivable. If you feel peaceful with your decision and you feel it is right that should be helpful.