Well, from all you've said, I think maybe this girl isn't quite old and/or mature enough for any kind of serious relationship. You can keep being her friend, of course, but it sounds like anything more involved would be highly risky and likely to fail.
It might be tempting to think that you're the one who can "fix" her, but that's just not how it works. She won't have a serious relationship until she's ready. And that could be years from now.
PJ
