Toxic friendship

I feel like I'm in a toxic friendship with my best friend. she has been acting jealous of me just because I get good grades. she always talks to me in a sarcastic manner and responds quite rudely. we were leaving class today and all of a sudden she just tells me to leave her alone and went to talk to someone else. she tries to make me isolate myself from my other friends just so that I can depend on her completely. I do help her a lot with homework and other stuff.Even after being there for her during tough times, she calls me derogatory terms if I accidentally forget to send her homework. she refuses to help me even once. Im trying to avoid talking to her as much as possible but she is like a leech trying to suck the peace out of my life. I honesty don't really care about friendships or love or whatever because I have other priorities but this bitch is on my every single nerve.i want to lash out at her but the problem is i have always been kind to everyone all my life. I know Im getting manipulated and I'm really confused on how to deal with her. plssssss help!