At a certain point, when the person in question has repeated the same empty apology, done the same manipulative act, hurt you in the same way over and over again, that you just need to get them out of your life.
Sometimes, it isn't worth it to bring it to their attention. Confronting them about it will only create bigger drama and you'll be back at square one.
Whether they are a friend, a significant other, or even a family member, cutting them out of your life-- emotionally or physically-- is the only thing left to do.
You can cut them out emotionally. Decide with yourself that they're not going to be your friend anymore, but still act cordial to them in a social setting. You may still have class with them or have to see them often.
You can cut them out completely. Pretend like they don't exist, don't think about them at all, and train your brain to repress memories of them. Therapists would say that this is not a healthy coping mechanism, but when someone has hurt you so badly, what is there left to do?
Toxic people most often will not learn from their mistakes. You can try and tell them what they did wrong all you want, but they're just going to tell you what you want to hear, be "better" for a while, and go right back to their old ways. You're then stuck in a cycle of manipulation. The point won't get across to them until it's too late, when you've distanced yourself completely and moved on from them and they realize how much they liked having you in their life, but you didn't like having them in your's.
You have to do what's best for yourself and your own well-being. You can't put your own mental health down for the sake of someone else's, not when that person really doesn't care about you or your happiness. So, don't feel bad when you wake up and realize that you suddenly don't think about that person at all. Don't feel guilty when you can all of a sudden breathe easier in a situation you once felt like you were drowning in.
You did what was best for you, and that's all that matters.