Please help me.

So I’ve been best friends with a girl for almost 11 years now. Last year she started to get on my nerves so badly that I sometimes cried when I got home because I was so pissed. My other friend feels the same way because she is sometimes so mean to us. She does nothing than complain about everything and brag about her family and their money and that her sisters are so successful. Now I have all my classes with her and there is no way that I can switch so I’ll have to deal with her for the rest 3 years ( if you are confused I don’t live in America )

She makes me feel really bad about myself and she is one of the reasons why I have self esteem issues. She always wants attention and compliments from everyone. She expects me to listen to everything she has to say but when I talk she just comes with short replies or “okay...?” “I don’t really care”

She also wants me to help her with everything because she doesn’t pay attention in class so I have to take my time to help her but she doesn’t want to help me. And today she told me that it may not be a great idea for us to have all of our lessons together because sometimes she thinks I’m annoying.

Me and my friend have talked about this several times, like how do we cut her off. Since I have to see her every single day and she is extremely clingy I don’t know what to do. My other friend goes to another school so I’m all alone with her. I don’t know what to do but I can’t stand her. I don’t want to tell her straight up like I don’t want to be friends with you anymore because I don’t want to be rude. But she follows me everywhere so how do I get rid of her. Please help me.