Okay, I did what most of you suggested and tried to stay away from her as much as possible since she didn't feel the same about me as I do about her: but she still acts soooo friendly towards me. She still flirts with me like we used to whenever she sees me in the hall even when i act like i don't see her. What now? Thanks for the replies and help! I truly appreciate it!

Why? Because!
Women (we) know when a boy is trying to or giving signals about love. If you told her, and she actually knows, then if she is trying to be nice to you is because something is happening inside her. I can tell you that (in my experience) when we say no to a boy, we start to think more often about him, and that is nice, because sometimes we fall in love. We start thinking about them and suddenly fall in love.
In the other hand I can tell you that sometimes eyes can not see what heart does, so if you still in love with her, it is much better to stay away for a while and then you will know if she really wants you back.

P.S. I am not supposed to tell you girl stuff

Well now you have to be honest with her and tell her that you feel like she is leading you on. She has already told you that she doesnt think of you like that but tell her that her body language is saying different.