Lost my bestfriend please help?

kso thiss girl that used to be my bestfreiend was like my sister over the summer. we even lived togther and we did everythig togther and told eachother everything and she became part of my family. she always went with me when i did things with my family and same with me and hers. her parents became like mine and the other way around and she was the closest friend ive ever had. then when school started agian we kinda drifted apart. we only hungout every once in a while instead of 24/7 but we were still close as ever and one day we were supposed to hangout but she started saying i was annoying and stuff and we ended up not hanging out after that. since then every time i asked her to hangout she would make up some excuse. and when i would go to partys and stuff and she was there she would litteraly completley ignor me the whole time and if i tried to talk to her she would give me additude and walk away and she would always say weird stuff on her facebook about this girl that was a and she hated her and stuff but whenever i asked her who she was talking about she wouldnt tell me. and she has a history with her other friends and me of getting really mad at them but not saying anything. like her and this other girl have been friends for years and she got mad at her and she told everyone she hated her and all this **** but she wouldnt tell the girl she was mad at and she pretended to be friends with her whenever she saw her bc she "didnt wanna deal with the drama" and shes doen this to about 3 or 4 people that i know of. and to me once for a few days. but now shes acting weirder then ever towards me and stoped anwsering my texts when i wanted to hangout with her and stuff so i started asking her are u mad and she goes nah then stops anwsering me so i was like whatevr hopefully itll blow over. well its been over 3 weeks now that we havent talked and a few days ago i texted her like 5 times saying why are u mad at me what did i do and stuff like that and the next day i sent her a long reallu nice message about how she was like a sister to me and i didnt want to loose her and asked her to stop ignoreing me and tell me whats going on and she never anwsered. the yesterday her mom shows up at my house with no warning which is weird bc our moms are good friends or used to be and she didnt even call andi open the door and says****(the name of my friend) needs her shorts and her sweatshirt back. she said she left them here and she asked for u to give them to her a million times and u never did so u need to go get them now. with like the biggest additude sso i went to go get them and i saw my friend or ex friend in the car and i went out and asked why are u mad at me and she goes im not and i said then why dont u anwser my texts and she goes i didnt get them and the whoe time shes looking down at her phone nd wont even lookup at me so i just walked back into my house and started crying and i called my firend nick and i was talking to him and he was telling me how she talks **** about me and stuf so i know for a fact shes lieing about being mad and i really dont wanna loose her as a fried. not only that if im not friend with her i wont be friends with anyone in my group anymore bc when shes mad at one person or anyone in the group is mad at one person they all get mad at them and pretty much everyone stops being friends with them. ive seen it happen bfore and i really dont want it to happen to me bc idk who else i would be friends with. idk what to do. please help (sorry this is so long)