Why did she do/say this?

I gave a girl with a boyfriend a flower and anonymous note for Valentine's. She's a girly/talkative type but kind of a loner.
We were friendly with each other but not friends.We had a mutual friend she always sits with, same classes, and lived next to each other.I'd joke with her friend so she knows I'm funny and can sing/dance, She definitely had a good impression of me.

After I told her I gave her the gift, she started paying a lot of attention to me.She'd look at me directly while smiling and observe what I do, and give me sudden, subtle looks.I walked into lecture hall once and looked up briefly to see if she was looking at me, and there she was, beaming--she was anticipating when I'd come.We didn't talk much but when we did, she was very hyper.

After a particular class, I like to walk back and she happened to walk back the way I do twice.The first time, she was pretty close and could approach me naturally, but for some reason, she called me when we hadn't exchanged numbers when she was behind me.Before we parted, she said she'd visit.The second time, I was almost home already, so it looked weird for her to be behind me again, so she tried to take attention away by calling people while walking fast to catch up.When she was at my side, she called another person then walked in front of my way, so I had to stop. Then she just said she'd call back and said "why aren't we walking.."

Considering that I'd indicated interest in her with a Valentine's flower, was she interested in me? She didn't find it awkward at all. I could have done stuff with her if I'd wanted. She never mentioned her bf to me. Or since she's in a long distance relationship, did she just want attention?

Well yeah! Of course she's going to act like that if you gave her a gift because she wants more gifts.

If someone gave me candy, I would be nice to them so I would get more candy.

If a teacher/professor gave me an A, I would be nice to the teacher so he/she would would give me more A's.

If someone gave me money, I would be nice to them so he/she would give me more money.

Plus, this girl has a boyfriend. So hands off if she has a boyfriend. Don't even go for her. Don't be a girlfriend stealer!

maybe you shouldve kept your gift to her a secret but ANYWAY don't let yourself be branded as, like Raze says, a gf stealer. she's taken and maybe she'll be like this even more so cos it's long distance. don't let yourself be used/ involved with her.

are you guys saying she was just using me for attention? or she wasn't really interested but just had some kind of obsession?

I was hands off.. if she wasn't interested and only liked the attention/gift, I don't think it's right for her to approach me like that without telling me we were just friends

well remind her that you're just mates and i agree with what you say. for future referance, keep your secret presents secret for once. and good luck :)