How can I handle this 13 old year old bad behavioured girl in this class?

The boy is easy to manage and it's very easy to get him motivated and engaged. But for the girl then it's a bit more difficult. In group discussions, she contributes very well and I ask her question related to the work and she can answer them. She also gives relevant points and ideas for discussion. I really like them and I like the discussions we have.I really like them and I like the discussion we have. The thing is she doesn't write them down and it just looks like she's been talking all this time. Sometimes when the teacher is talking, she will turn around and talk to the boy which distracts him off his learning. She also was touches the girl's stuff behind he and pushes the boy next to her because she is frustrated with something, but I don't know what she just randomly does it and I don't know why. Whenever I tell her to stop, she gets annoyed with me and doesn't speak to me and tells me to go away and stop going near her. She gets very frustrated with me and sometimes tells me to shut up and that she doesn't care. I just ignore her.She says go away and tells me that her dad is 6ft6 and is a boxer.
Update: I ask the group a what they think the question is on the board and she just thinks I changed the subject because I was nervous. She is a nice girl when she's not angry and she does like me because I heard her ask for me before the lesson. I'm 16 and have no teacher assistant training.