Why do I keep dreaming about an ex best friend?

She was terrible to me, used me a lot, and just made my life a lot more stressful than it should’ve been. I know I don’t miss her, so that’s definitely not a reason. In my dreams she’s always trying to be my friend again and I’m yelling at her “get the f*** off of me” or I’ll yell “I hate you leave me alone” and I’ll shove her off. I’m not even in high school anymore and I don’t want to keep dreaming about her.