I personally think it's irrelevant what you believe, it's respect that's relevant. And respect is a two way street.
Is there no way you could go and have a good time whilst respecting her reilgious views (as is sounds like you do) and have her respect your views not to take part if you don't want to?
I may have missed something, I've been at work for the last 24 hours, I apologise if I have but that was my thought as I read your post.