[18/m] I love a girl (19/f), but I'm in an atypical friendzone. Go for it or don't risk ruining the friendship?

She's amazing. Funny, super cute. She likes me, a lot, and we have a lot of physical contact. The problem is her family is super-Christian, and she, while not a fanatic, is very religious. I'm an atheist. It doesn't really bother her, and her religion doesn't really bother me. But it has restricted the bounds of our relationship.

We talked about the possibility of dating, and the way she sees it is that the relationship will never go very far, i.e. marriage. Not that she wants to go into a relationship only if she thinks she'll marry, but that she thinks that we can never break that barrier. She agrees that we'd be great together, and that we might date for years, but that eventually she KNOWS we would never go further than that.

My opinion is that we should take the happiness while we can get it. She doesn't want to go into a relationship knowing it will end, which seems pessimistic and a little illogical to me. Love is about risk, and in my opinion you go for it and if it hurts in the end, the happiness was worth it.

I think that she thinks we're done talking about it, but I'm thinking about bringing it up again. Should I risk losing her friendship, which I don't really think would happen, but would be awful, in order to state my argument better?

Additionally, I'm totally not good enough for her.

TL;DR: She doesn't want to go into a relationship knowing it will never go to marriage. I think we should take the happiness while we can get it. Risk the friendship to state my case better?