My "friend" is extremely rude to me

So I have a friend that is in the same year as me (we are 16 in high school). I am sorry in advance if this is a bit long, but please bare with me. We have been friends since that start of this school year (she is a new student) and I once thought that she was my best friend. I was always kind and respectful to her, and she used to be somewhat of a good friend, but now, she constantly insults me and she is extremely rude / disrespectful!

It was only recently that her rudeness escalated and now, every single time that we talk, whatever I say, she ridicules it. She says that I'm "annoying" and that I don't know anything. (Btw, I am also her only friend at our school, yet she is so horrible to me.)

Even our English teacher noticed, and she asked for her to be less harsh on me.

Today was the point where I just had enough; we were eating our morning break and she asked me in a very harsh voice "go and put back my cup of tea". (We have mugs that we have to put back once we finished them.) I always did that but I was sat down and she was already up, so I just said "no". She then continued to ask me in a rude way, and I just responded, "I am not your slave, go do it yourself". She then continued to argue but I just walked away in the coldest way possible. She then came up to me and ranted about how I was rude to have left her in the cafeteria alone.

Here was where it got really bad:
This afternoon, we had to work on this presentation with another one of my friends. She began to insult me again and told me how I'm useless and that I should just "shut-up" because I apparently was incapable of bringing information for our English presentation. (She also said how she does not want to add me or my other friend in the credits since she didn't even let us contribute to the presentation.) She continued (by the way, the teacher went out of the classroom for the whole lesson because she had an important meeting) but then, the other friend that worked with us just had enough and said "Don't talk to Alex (it's me) like that, you are being very mean and rude!" and then, my other friends began to tell her "he didn't do anything wrong, stop being so rude with him!". I am so thankful to have such great friends, and she just did not talk for the rest of the class.

I also went with my other friend to talk to the teacher and the teacher told us that she will talk with my rude "friend". We can now make our presentation (only the two of us working together without my horrible "friend").

I am so sorry for this being so long, but what should I do? My friends began to notice that she was being mean to me since last Friday, and they all told me to distance myself from her. (They all say that it's unfair to be treated like that!) I had enough now and I was patient, but she is just disrespectful and shameless of herself! Thank you very much for reading!