What should i do? bestfriend fight!?

ok so i was dating this guy and i really didnt like him but he gave me a necklace so i felt really bad...i didnt want to break up with him cus he was sweet but i liked it better when we were just friends...so the guy i really liked asked me out and i said i had 2 break up with kendall(kendall is the guy who gave me the necklace and nick is the guy i liked) so i called kendall and we did 3 way wit my bestfriend but he didnt answer so i was goin 2 break uo with kendaall monday but nick thought we were already goin out so everyone thought i was cheating and my best friend said the same thing and that i used kendall but i did like him for a few days till i decided i couldnt so i admited to her i kinda used kendall but she got all mean so i told her she used boys too cus she went out with a guy named leo and she didnt like him at all cus she told me and she just went out with him cus she had come out of a bad relationship and she wanted someone but she just used him and broke up with him the 2nd day they went out so i told her she shouldnt tell me anythin when she was guilty too so she stopped talkin 2 me and shes got these 2 friebd kayla and summer and durin free period she was talkin bout me and tellin them things bout me and kendall but that night she appologized and i thought we were friends again but then today i had this celebration for makin my A.R goal and i asked the teachr if i had to go and shes like "i just spent 2 weeks plannin this so im goin 2 pretend i didnt hear that" and im just like ok and then when i went to luch my best friend was like in a bad mood and she wouldnt talk and i always bring my math homework to lunch cus she helps me with math cus i suck at it and i asked her can u help me w/ this 1 and shes like idk.. and im like r u mad @ me or somethin and she said not really and i know her so i knew she was so i said tell me and she wouldnt cus she said she knew i would get all mad so i finally got her to tell me and she said i wasnt appreciative because i didnt want to go to that celebration and i asked the teacher and she said i was always in a bad mood and that i USED HER FOR MATH HOMEWORK CUS I NEVER DID IT AT HOMe i was shoked and hurt and shes the one whos always mad and get aggrivated at me and i just deal with it and also she goes through these phases where she is best friends with different people and shows off about it but i actually deal with it cus shes my friend and tomorow we hav this huge test and we usually study together and this afternoon i decided to call her and i said "do u want to study together" and then she just said "im actually done with my studying" i just said okay.. and hung up but i want to stop fighting cus this is our 1st fight but idk what to say.. help me!!!!!!!!!!!!!!!!!!