TL;DR at the bottom, this one's quite long

Ok so from the title this must sound pretty shitty. But before you judge me, there's some backstory.

Last summer (around june or july), I was in a games lesson (I'm a 14 y/o male) and one of my best friends (we'll call him A) and a girl from my year (we'll call her F) are talking. Now, I used to have a crush on F the previous year but have never spoken to her, however I think she knew about the crush because she's friends with A. Anyway, I join in and at the end of the lesson I walk home with F (as I walk along the road she lives in). For the rest of the school year (which is about a month) I start hanging out with the rest of her friend group. There's a smaller group (consisting of F, A, a girl and a guy we'll call AS) which sometimes hang out with a bigger group (there's like 30 of them I won't bother naming them all). I tend to get on with the people within the smaller group, however in the bigger group they often act like they don't want me to be there. I'm really insecure about my relationship with them as I feel they're too "cool" for me and that they don't really like me. The smaller group have a group chat with me on. 

During the summer holidays, we discuss maybe watching a movie, however AS (he's super rich) wanted to go to this fancy restaurant in town and sneered at me when I suggested McDonalds. After this I went non contact with them until september (not intentionally, but that's another story).

When I am able to rejoin the group chat, it's dead. By that I mean no one ever chats on it and no one ever responds to me. I learn from A that the group made another group chat and that they talk shit about me on it behind my back. That evening over text I confront F. She doesn't respond for a few hours so I send a text calling her a "manipulative bitch". She says "if you were a sane and communicative person...". This really annoys me as I have aspergers and she is calling me insane. She also calls me "hopeless" and "difficult". This was in around October. After all this A denys ever having told me that they talked shit about me.

I felt like a total arsehole after, and so I sent her a message saying how horrible I was. She couldn't even be arsed to reply.

On Friday A was talking to F and A asked me why I was such a dick to her back then. I need to know, Am I The Asshole?

TL;DR close friend betrays me by making another group chat in without me and talks shit about me behind my back. When I confront her, she doesn't respond. So I call her a "manipulative bitch". She then mocks me for having a mental illness. When I beg her to forgive me, she doesn't respond.