Relationship Advice: Did I do it wrong/What should I have said?

I’m 18 and my girlfriend (17) of 2 years told me she wants to go to church. I am… not exactly an atheist but close enough, for this argument. I have told her before that indoctrination is a huge deal-breaker of mine, if you want be be religious then go ahead but don’t bring me into it. She asked me last night and I told her I didn’t want to go and she knows I hate religion. She said either go or break up with her because she needs to stop having sex with me (yes it is legal, AL consent is 16 and no, she’s not my sister, thank you) and turn her (our) life around. I told her I would sit with her if she wants but I wasn’t going to listen to the sermon and I wasn’t going to care about it, but I’ll go for her sake. She got angry and told me we should just be friends, because, and I quote: “She doesn’t want to be with someone who won’t take her attempts to better her life seriously”, and that she just wants to help me be better. I’m summarizing of course, there was some yelling and personal verbal knives over the phone. I know I shouldn’t have been so cold to her but I was so appalled that she even asked me. I’m not asking sarcastically or looking for people to validate my actions, I just want a third party opinion: How much did I do wrong?