First of all, I would like to say that this situation is strange, but not necessarily impossible. Just because she is a Christian does not automatically mean she will not be accepting. In fact, I am a Christian, as is my family, and my parents were perfectly accepting of me, as were all of my Christian friends. So that MAY not be an issue, though depending on the person, it might as well be.
But like Devlyn says, if it will happen, it will happen. And that's all there is to it. There is hope, though, trust me, man. Best of luck to you. If you two start getting serious, though, you definitely need to tell her and not live forever in stealth. You don't want to start a relationship based on half-truths.