why would you want to be her friend anyway? She obviously doesn't want you to bother her that is why she is being unfriendly to you. She has problems, so you should take it like that and just forget her and stop trying to make the situation more complicated than it is.
Some guys just can't accept "i am not interested" as an answer
I hate when guys don't take the hint, its like they want you to yell at them, drill it in to there head, make a scene, and embarrass them before they finally understand and then you would only call her a "Mean Stupid Bitch!" when she does decide to do that.
The reason why she is not yelling at you and trying to embarrass you is because she believes that it really is not that serious of a situation and you should have understood that she just does not want to be bothered, also she probably is not a "Mean Stupid Bitch"
to summarize, if a girl wants to be approached, then she will make herself approachable and you would not even have to analyze because it is that obvious. If she does not want to be approached then she will make herself unapproachable and is trying her best to not be noticed because she has problems or just other things on her mind, so leave her alone, and don't think about her because that is what she wants.