It doesn't seem like a smart idea, she might be planning to rob you or falsely accuse you of rape, and even if she isn't, she's probably just using you because you seem a low-danger alternative to whatever she is running from and isn't planning on rewarding you.
If she ran away from home, her parent will probably have you charged with kidnapping and statutory rape.
My instinct is "well, maybe if I can trust her..." but I should question that instinct. Even if I feel trust, that's just because I'm conditioned to trust women. It's not necessarily a smart idea.