How can i get her to back off ?!?

Well theres this girl called Jess, and she's my best mates other best mate. She has never really liked me and i have come to grips with that, i don't caree tbh! However, she always pes comments to me and gets involved in things she should really stay out of. I DON'T like herr at all and i am sick of her getting involved in everything that goes on, either with me alone, or me and my best mate. How can i get her to back off?? need some good things to say to her!