Do u think she likes me?? Plz help for 10 points!?

There's a girl I've known for about 3 yrs. we meet rarely but whenever we do, I ALWAYS catch her CONSTANTLY STARING at me straight into my eyes. She makes very very long eye contact when we talk and smiles a lot. One day I gave her a complement on fb n she immediately replied . Then I tried to push d conversation ahead but she simply didn't reply to my msg I sent her . She really stares me a lot and gives prolonged eye contact with a smile. She has a bf and she even has given me a nickname between her frnds, bt she never told me about the nickname thing. Why is she doing so???!!! Plz help!!! Thanx everyone! :)