Walk away.

A good person she certainly is not, she's mean and abusive. Hall mark trait of an abusive person is that they know how to say all the right nice things to make their victims believe they are actually good people.

Good friends don't treat you as inferior, they treat you as an equal, good friends don't discourage you, they encourage you to do the best you can. Good friends don't belittle you and invalidate your problems, they listen, empathize and support you.

The "friend" you have described is toxic, don't allow her to poison you.
Life is challenging enough without us having to give people permission to treat us badly.

Follow your best friend's good, healthy example and just walk away from this person.

Walking away doesn't mean you're a bad person, or any other negative thing you may believe when you feel guilty.

Walking away means you're smart enough to value yourself.