I have had this dilemma before. Just ask her. You never know what she will say. I would suggest that you drag it out a little, I mean, act nice to her and all, do all the good stuff.
I just asked the person straight out. And guess what happened?
"I just want to be friends".
Ah well, you will have to put up with these things in life, if she says yes, you're all cool. If she says no, you're all cool anyway. Just take the chance. If you don't, you might soon find that that chance is gone. That what will you do?