What does this mean? why does she do this?

Ok, so there is this girl that i hate.. and she doesn't like me either. well, when we played our bball team together, we got in a fight in the middle of practice.. long story short, i got kicked off.. well, the next semester, she had to take a cl with me(she's like 2 grades ahead of me) and she sat right behind me. just recently, i noticed that she was playing.. i guess " footsies" with me? whenever i moved my foot, she would kick it. not hard, just enough so i moved it. now she does it constantly. i don't know if she does it on purpose... and when i finish, say, as worksheet, she pracically tells me to give it to her .. and i feel that if i don't, i'll regret it. usually i do defend my self,... nut she has this "subtle" way about her.. i ts not really harrasment... ao what should i do? why does she do it? my friend pointed out that she thinks that this girl might like me... and she is bi.. is this her way of flirting? what do you think??