I've known this girl since she was my Spanish partner in High school (2 years ago) and now were both going to college. I'm 2 years older than her. Well anyway, I started to like her alot and I frequently look at her. I notice that she usually looks back at me and holds eye contact on occasion( and smiles). I tried to add her on Facebook, but she denied it. I visited where she worked last week and she seemed a little nervous, but she said Hi to me, and then she talked with one of my friends who also works there. I was in on their conversation though and she frequently looked at me. The way she acted definitely showed that she doesn't dislike me. Anyway, she still looks at me often but I don't get why she didn't add me on Facebook. My gut feeling tells me she likes me but I'm not sure anymore.

What do I do?