One piece of advise from "The Tao of Steve".
"We pursue that which retreats from us".
Sounds to me like you guys already have a pretty good relationship, not sure if your in school together or what. You should take some time and get a little spearation from her. Now I'm not saying to go out of your way to ignore her, that would just be rude. But make an effort to not be around at those times she expects you to be there (for like a week or so). If she has "feelings" for you then most likely she'll wonder where you are, and maybe even miss you.
After above time period has passed, you should (maybe) be able to gauge her feelings from her reaction to your "return". If she says "Oh, I missed, what have you been doing, etc" Then I say tell her. If she says "You were gone? Oh, that's right, I forgot". Then I say don't do it. Train wreck waiting to happen.
Again these are just my opinions, I could be totally off base.
Pebcak