What do i do if my friend does not undertand me?

background info-Ok i am having problems in school with my friends. i am in grade 12 and my cl room has only about 15 ppl in it and we have all known each other for along time now about 8 years..one of my friend a girl started to date anoter one of my guy friends who i really wasnt tight with be4 but now he is a very good person adn hes like my big brother and very understanding person...on the other hand my girl friend is very selfish and egoistic and doesnot care about others feelings too much adn just thinks she is alwasy right and perfect so thas y my guy friend broke up with her since she use to beat him up adn always fight over little things and now he had enough and broke up...the problem now is that im tight with both my friends adn my girl friwend wants me to froget about my bro/friend if i am a true friend to her...i feel bad for her and i have bin fullfilling my friendship for more then a year i mean i even for i even fought wiht my otehr friend for her and now me and my best ffriend since kindergarten have been too nice to her and given her alot of poewr in cl and she is like controlling us practiccally we are herbitches but i dont want to say sumthin to hurt her feelings but i am feelin like a dog being controlled plus i dont want to loose eother of my friends they both mean alot but i am tired of me doin **** for her like she tells me to talk i tlak if she says dont i dont but i dont want to be mean plus i need answrs fast i have tried to understand her alot and she has nvr understood how i feel shes alwasy rude and disrespectful to me but i am still nice plus plz i need to solve this problem before tom cuz tom my birthday and i dotn want to ruin it adn i want evrythhin back to the way it was be4 veryone happy plz sumone hlep me :(