Bf is flirting with a girl who h8s me!?

ok so im 13. i like my bf sooooo much!!!!!! BUT theres this girls who sticks her cheast out and she hates me cus her bf thought i was hot. so my bf and her walk off talking and flirt and he puts his arm around her and i tould him it bothers me. then my bff was at the vollyball game and he came to watch and he put his arm around her, its soooo anoying just cus im not there dosnt mean anythin different. so i mite breakup then wen he sees that im serious hel try to get me bak.. idk i need help. i like him soo much. iv tryed taliking and it dosnt work