My sister and I despised each other for a long time. She had ODD (Oppositional Defiant Disorder) and ADHD which caused her to be extremely violent and downright mean until around the age of 9. She attacked my parents as well, but her violence towards me was the most frequent. She bit me, spit on me, intentionally broke my toys, punched me, etc. As a kid, I was not good at defusing arguments, and I would argue back with her, which often let to her assulting me. This back and forth and constant fighting caused us to hate each other for a very long time, until she eventually grew out of her ODD and violent tendencies, and I matured enough to learn to control my emotions.
I put in a lot of work towards fixing our relationship. I try to be nice to her, even when she insults me. I take her to get Starbucks and go shopping which I buy with my own money. We play games together and I often drive her to school in the morning so that she doesn't have to take the bus. I do pretty much everything I can to be the big sister I wished I had growing up.
I really thought that our relationship was in a good place until a few days ago when completely out of the blue, she tells me that she talks to her friends about how much she hates me. I was so caught off guard by this. We have our fights sometimes, but I really felt like we were in a good place now. I told her how hurt I was by this, and she apologized, but the fact that she feels this way in the first place is crushing. I'm still mad at her about this, but I've been keeping it to myself for the past few days. I know she's still very young and may change her mind in the future, but I just feel like all of the work I've put in to fixing our relationship has been pointless and I don't know what to do to get her to like me.
TL;DR: After years of fighting, I thought my sister and I were finally in a good place, until a few days ago when she told me she frequently talks with her friends about how much she hates me. This news was really disappointing to me and now I feel like there's nothing I can do to get her to like me.