Our mate is a mugger?

well me and my 2 best friends have a friend but since a new girl has come shehas mugged off with her and picks on us and has been a total ***** and does my headin and if we say stuff to her about it she will go in a mood and she acts good in front of her but she isnt and she does my 2 best friends headin like always and if she falls out with the new irl she will run back 2 us !!!!