AITA for excluding our "friend" from our girls group without telling her why?

We are a small class with 16 (female-only) students and because we study a niche-y subject, we have all classes together. The first two years were very intense with 8 hours of lectures every day so we got to hang out a lot. Although we all get along, we have formed smaller friends groups. I am in a group with 3 girls. Two of them a my closest friends. We spend a lot of time together. But number 4, who is also in this group is really annoying. I used to be friends with her too, but at some point I noticed, that the only two things she ever talks about are herself and her fiance (whom we all can't stand because he is sexist and the most entitled person I have ever met). This man is literally the only thing she will talk about and even when we show obvious signals of disinterest, she doesn't notice at all because she's so self-absorbed. Also she is always defending his sexist opinions even tho she claims she is feminist. She barely asks me how I am doing and if she does, she'll listen for 2 minutes before she starts talking about herself again. It wasn't like that in the beginning, she used to be interested, but in the past year this has shifted and I really just cannot stand her anymore. I asked the other girls what they think and they also noticed how annoying she became. I kinda told her in a nice way that she needs to change some of her behaviors, but she doesn't really get it. We are still meeting up, but without her. Normally we dont tell her but sometimes she hears of it so we make up excuses. She also asked multiple times in our group chat, if we want to meet up with her and we either said that the timing is bad or didn't reply at all. We think she notices that we are excluding her, but she doesn't know why. I honestly don't want to talk to her again because she has this habit of blaming others for her mistakes. For example: I told her a few months ago that she need to educate herself about racism because she said some racist things to me, repeatedly. She apologized for the things she said but also told me how "hard it is to be white, wealthy and heterosexual, because no one tells you how privileged you are". I can't with this girl. She also never admits any mistakes she makes. She always acts like she is perfect. So I'm really torn because she used to be my friends and we are all noticing that she is making an effort because she doesn't know why we exclude her. On the other hand, I don't think she would understand if we told her why and get all defensive and arrogant. And my other friends don't want to say anything and are hoping that eventually she will notice on her own (to be fair, she said the exact thing about a person who kinda did the same thing last year: to just wait, she will notice it herself) We have another 2 years of classes together and I have to take the same train as her every morning (and obviously she noticed im not sitting next to her anymore). AITA (or better say: we) for just excluding her without saying anything?