Should i be her friend ?

My 15 year old friend is negative and quite immature about everything and everyone and doesn't like the "popular" kids, she tells everyone to shut up or starts swearing at them so nobody wants to be her friend and nobody wants to be my friend because im associated with her and she is always with me so i don't have chance to make other friends because of this. She is alright with me though unless i say a joke she doesn't find funny and then she would storm off. The reason she is angry most of the time is because she has a boyfriend who she is having a long-distance relationship with, someone who i have never met and talks to him constantly on the phone when i am out with her and they keep breaking up so she cries to me i tell her to dump him but apparently she is too in love with him and then they would get together again and the cycle starts again. She never listens to my problems and when she does she offers me solutions like swearing at the person and i tell her im not saying stuff like that and she says im too soft on people and shouts at me. It is starting to get on my nerves she has lots of problems but im not sure what i should do. Can i help her somehow or not be her friend at all?