I'm having some friend issues...help?

In my A.P. English cl today we had to read essays we wrote on a controversial issue. One girl starts to read hers and it's about people being punished because of their religious beliefs. Well my friend turns to me and ask me if I've seen the move "The Da Vinci Code" She starts talking about the albino guy that hurts himself. She says its because he's killing people. I say, "No, its because he is Fascist(?) Opus Dei. They punish themselves because of how Jesus was harmed on the cross." She says no. And i try to explain. Now even if I'm wrong and that's not the case is it right for her to turn away from me? She wouldn't even let me explain. Religion and politics have always been a touchy subject with us. But this has nothing to do with that and she had no right to turn her cheek to me. Especially when she knows how much i hate that. It was really rude and its not like the first time she's done this. When ever we get on something she doesn't want to talk about she does that. And now its really starting to piss me off. We've been friends since the ninth grade, we're only juniors now. But lately it feels like we're growing apart. I don't want to loose he as a friend but whenever i try to talk to her about something that she doesn't exactly agree with she does that. And if there is one thing that makes me really upset, its being cut off in the middle of a sentence and not being allowed to explain. Help please.