What do about my obsessive friend?

Let me start off byt saying that I'm a 14 year old girl in 9th grade, and there's only a few days of school left. My school is small and everyone knows each other, so if you did something bad to one person.. Most of the grade hates you, which is my case. I have about 8or 9good friends I can trust. My one friend who I have been friends with for 3 years (abi), is a very good friend to me most of the time. Last year I got into this huge fight with her and some other girl(Emily), making her hate the other girl. Anyway, Emily started telling me not to be friends with abi in the beginning of this school year, which really pissed me off. So I told Emily we weren't gonna be friends if she kept annoying me about my friends. Well, that drama went away and all was well up until about a month ago. My friend abi started not liking our mutual friend, Alex. So today at lunch, I was talking with abi about my birthday party id be having. She said "you're not inviting Alex right?" and I was like yeah I am. She said if Alex was coming she wasn't coming. And she started telling me that me and her were better than all my friends and for my birthday I should just go shopping with her. And I was like.. Okay whatever. But I talked to my mom and she was like, no you're having a party. And Alex and I have had fights in the oats , along with my other friends but we've gotten through that. And I want to have a birthday party but abi is getting so mad at me and YELLED at me today so what do I say to her? Thanks for your time :)