Why is this girl so rude to me?

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. She used me as an example once and was like imagine him driving while talking to her friend. 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.