Is this the right thing to do?

My best friend has been getting stranger in the recent years. We've made plans to meet up and I've invited her to my house on numerous occasions but she always flakes out last minute and makes the most daftest excuses as to not turn up. Even when I ask her about making plans she always says we will and makes false promises but she never does. So when I try to plan things she always turns the question on me when I ask when she's available and then proceeds to come up with another excuse for not going out. I'm annoyed because we are supposed to be best friends but she never wants to meet up with me and meets up with every random person from sixth form instead (we're in uni now) and she has accused me of things but after confrontation she starts apologising.

She says one thing and does another, we say we're always there for each other but when I send a serious text or bring up a serious topic on the phone - she straight out ignores it and talks about herself instead, acting as if she doesn't believe me or doubting my words.

In the past she has also done this; says one thing ;does another. I remember her birthdays and graduation days along with other important dates but she never remembers mine - when she realised she forgot my birthday she started arguing with me and saying my birthday was on a different day - like wtf?! After seeing me upset she will always always try to bring up a sad story about her family so I feel forced to console her. I don't know what to say and I'm starting to recognise this manipulation.

Then she asks me why she hasn't got any friends left, because she's been ghosted a lot and it's only now I've started realising her true nature. But now she's gone and done it again - everyone around me has told me to stop being friends with her, because all she does is mess me around and there's so much more to this - but I just feel like not messaging her anymore and spend time with my friends that are there for me. What should I do?