Friend problem?

ok so here's the deal .there's a friend of mine (so called friend)who is a real rudy and thinks she is the leader of our group and thinks she is really bold and can beat anyone anywhere she likes.she doesnt even do anything when i tell her to do something about the lices in her hair.i have always been really kind to her evn when she took my lunchbox and emptied it and when she banged my head on my own desk.i don't know why is she like that because she belongs to a really good family and i also dont know why i became friends with her.i have stopped talking to her.is this the right thing to do?is this the solution for all problems?