Please excuse me if this sounds incredibly corny, I'm trying to get all my feelings out as this is something I don't confide in anybody about, but it definitely sounds like I'm just really edgy.
I'm 16F (assuming that will be relevant somehow like maybe this is normal for teenagers I don't know) and relatively recently I experienced a large betrayal from my best friend. I cut her off for it and slowly, in my time away from her, began to see her in a completely new light but at one point I was convinced into giving her another chance, which she exploited and has gradually become worse and worse again. I won't go into details because I always get incredibly angry just writing about them and they have little relevance but the important part is she isn't a good person. It may also be worth noting that at the time I was going through a breakup and my mental health was exceedingly bad anyway, so her betrayal hit a lot deeper than it would to me now, though I still would've been extremely upset now, and since she's come back into my life and clung on to me. I know how stupid it sounds but I can feel it like a physical weight sometimes. She was my best friend of 7 years.
Other struggles with my mental health have included growing up undiagnosed (now diagnosed as of a month or so ago) with autism and many complications coming with that such as eating disorders and depression. I've also been prone to pretty violent (not necessarily to people!!) and explosive outbursts when I'm extremely angry. I don't know if any of this will be relevant, though.
For the past month or so I keep thinking about harming her. For obvious reasons I won't go into any details but it just started out as just slapping her or something, but has escalated since then and now I almost obsessively think about really really hurting her and/or killing her. I am relatively sure there's no risk I'll actually do this, but I'm a little bit afraid that it might get to a point where if I'm really angry one day I won't be able to control myself lashing out at her (as incredibly corny as that sounds 😭). Id never carry a weapon and my anger wouldn't last long enough to suffocate her or anything she's in no actual danger but it still wouldn't really be ideal. The thoughts are very very graphic and sometimes Im actually afraid by them. Again, she's in very little to no actual danger, but I still hate that I can't stop thinking of them. What can I do?