What to do if I want her back..?

Last semester, a girl and I both started liking each other... We lived in the same dorm area, so she even chased after me twice after class just to be with me...she did it subtly but it was pretty obvious.

The second time she 'happened' to be walking back after class, I told her we should be friends, partially because I was a little intimidated by how aggressive she was being even though she had a boyfriend. Now I realize none of that should have mattered.

I really, really regret saying we should be friends, but at the time, being stupid, I thought that was the best choice and that it would be easy to just shut my emotions off like that.

Ever since, she hasn't been the same towards me either.. and it became a little complicated because neither of us knew what the other's intent was...
She never asked me why I wanted to just be friends with her...and I guess it's partly because she doesn't want to blow her cover that she was interested in me even with a boyfriend..

I am not sure how she feels towards me..i guess I'm not sure how to feel towards her either...but I would like to try again. We both try to act like everything's fine but I have the feeling she's not really okay...

Please give me advice on what to do. i will see this girl mostly in class sitting with a mutual friend...and probably hang out with her every now and then through the mutual friend. Should I be direct or continue to 'be myself'?