Why does this girl do this?

I sit beside a girl in class and i dont kno why she acts like this. She talks to her friends infront of me on another side of the class. I was in her way while she was talking to her friend and she was like move cant u see where talking. She sometimes talks to me. Also she helps me alot like does me favours and is nice to me and she smiles while talking to me. �Ill catch her looking in my direction and she quickly glanced away. When we left class i caught her looking back at mre. However one day she was mad cus i was gona copy her work and she moved away and said now you have to do it yourself but the next day she was talking to me. I see her talking to this other guy but we never talk outside of class.