My best friend is being really mean to me what should i do?

i'm really desperate :( ok, i went to a small private school, there were only 7 in my grade (6th) my best friend (Carlie) liked are best friend (Reid) we all sat at one table. Me and Carlie have been friends for 3 years. They were both really mean to me they teased me, called me names, called me gullible (ok so mabe i am they don't have to rub it in my face) they would leave me out alot, stuff like that. And Carlie's fave colors were green and orange, if i even dressed with one of those colors she'd get her face (she has this face that she gets when she doesnt like something she like rolls her eyes). And she thinks she knows when i'm lying I've lied to her once i said that i thought Reid liked her. Aand then when i try to disprove her when she thinks i'm lying she gets all like "why do you always try to disprove me". I've tried to tell her what shes doing but she denies everything!!! And one night when me and Carlie were having a sleepover i got her and Reid together, now there going out, i thout maybe, just maybe, that if i got them together it would all stop but no.they dont it mght have acually gotten worse :( i'm kinda thinking she's just using me to get to Reid, cuz i'm the only way she can see him cuz her mom's our teacher and shes kinda strict and doesnt no Reids mom. So i have to take Reid and Carlie to the pool with me thats the only way they can see each other, there not even going to the same middle school ( so i don't think it will even work out with them) but me and Carlie are. I want to not be her friend sooo bad but I dont think i could stand up to her and tell I dont want to be friends. Plus her B-day is coming up and it might be kinda weird to her mom if i'm not there. I'm sry if im spelling stuff wrong I'm jus so stressed i'v spent hours crying and trying to figure out what to do. I've even asked my mom!!! and i like never go to my mom with anything unless i really need her help. I've even asked ppl from some camps. And everyone I've asked says i should drop her. I've explained to Carlie and Reid that there being mean but they just don't stop. idk what to do!!! plz help should i just defreind her or just deal with it?