should i leave my friend??

i faced the same situation in my life 2 times. first time my bestfriend cheated me one of our common friend told me about this i talked about it to her in front of that friend and she refused. After some time i came to kow that my best friend is cheating me.its really hurting. i left frienship with her. in second case my friend told to one of my good friend that i say absurd thing about him. my friend didnt ask anything he just stoped talking to me. i am surprised from his behave. and one day i asked him why he is not taking to me he told me every thing i have not explained anything to him and just stoped talking to him. one day he came to know the truth that i am innocent but its to late. if he cant trust me then how can he say that he is my friend. so i suggest you to talk to your friend in front of your common friend. without knowing the whole truth please dont take any action.

It sounds like your "best friend" isn't a friend at all. Anyone who tells you no one else cares about you except for them, that is mental abuse. I am sure MANY people care about you, and you have other friends than this one. You should talk to her and let her know how you feel, find out why she says mean things behind your back. Why did the common friend tell you these things? Maybe she is your real friend. Or maybe she is just trying to cause trouble?