Beat my depression

It’s been coming and leaving for about over a year now. The people I care most for in my life are the main cause of it. My best friend of 9 years tried to sleep with my boyfriend about a year ago. “Sorry” hasn’t really changed anything. Karma needs to come around. I’m trying to get the negative people out of my life to make myself happy. And she seems like the only true negative person that makes me so upset every time I think of her or talk to her. I want to end the friendship but I can’t find it in my heart too. I can’t help but be loyal even to the people I once loved and now hate. So I don’t even acknowledge her existence now. The only time we talk is when she talks first, which is only if she needs a ride to school or to complain about her 27 year old boyfriend. She’s 18. I feel like she’s a sister that I can’t stand and want to fight with 24/7. But this is completely different. I don’t want to hurt her but I wouldn’t mind seeing her hurt by someone else.