Not trying to pin the sexism tag on you, but it really shouldn't be said like that.
From what I can see though is that most things to help you have been said already, that includes the "rudeness" of telling you to mature a bit.
You are mature enough to understand things, so that's good. You wanna "protect" people, sure as naive as that is, go ahead.
From how close you say you two are then it really i just something about time and about her wanting to take that kind of interest in you. I'm not going back to read if you already told her how you feel about her, but if you haven't already then that's something to be done because you're not getting anywhere if you don't
You should also really try to get to know this other guy, sure he sounds like an ass, but everyone is/can be. Who knows, maybe you two can be best buds...
Again, most things to help/"help" have been said, so I'm going to leave my stuff here.
If you're that determined then maybe something will happen, but it's best to not expect it.
