(Throw away account with different names for animosity)

I (15NB) am so scared of going back to my dads today but I want some advice on whether I made the right decision.

A couple of nights ago, I was upset about something (I don’t remember what though) which ended culminating in my mom (47F) calling my dad (54M.) my dad (unsurprisingly) didn’t answer but when he did call back, his girlfriend (53F) answered.

For some background; I am a needle baby and I stay with my dad for schooling since my mom and her girlfriend (30F) are looking for a house in my school district to move to so I can come back. I normally come to my moms girlfriends house on the weekends or breaks so it’s not like I don’t see both parents equally. I’ve known my dads girlfriend since I was born and was under her influence until 2020ish, when I found out how horrible of a person she truly was. I guess I had buried the memory for a while but back when I was 6 (the night I graduated kindergarten), she pointed a gun at my moms head but didn’t shoot only because I begged her not to; then proceeded to burn the house down with me, my sister (20F now) and herself inside all because my mom called her out on how bad she was.

Back to what happened a few days ago: my dads girlfriend (who I’ll call burnt Barbie here) was talking to my mom and lying again like she always did and it got to the point of me snapping. I ended up yelling at her about how she treated Harley (my sister) horribly for my whole life and how she was emotionally and verbally manipulative (making me watch her give herself diabetes shots to scare me) and about how I wish I had my therapist back before forgetting she wasn’t supposed to know I had a therapist because she would end up twisting a story about how “Tarry (my mom) is such a horrible mother, her kids need therapy.” I wouldn’t be this scared if it was mostly just this though I’ve never stood up to her before and I ended up bringing my dad into it. You see, burnt Barbie has my dad wrapped around her fingers though he has been getting tired of her recently. I ended up yelling about how she didn’t even care when my dad made me eat my own vomit and I hung up on her while she was talking since I couldn’t stand it anymore

For more context: back when I was 4, my dad made me eat some kid cuisine Mac n cheese even though I have texture issues with food and I threw it up. He then proceeded to catch my vomit and made me eat it, making me throw up again before he put me in time out for it. My mom was pissed when she found out about it but my dad denies doing it to this day (I’d I can remember the brand, I’m pretty sure it happened.)

The next day, my older sister Debbie texted me talking about how “it wasn’t fair that everyone was treating me like a prize to be won” and said “while she was a mutual party, both my mom (somehow) and burnt Barbie were in the wrong.” Talking about how my moms girlfriends get too involved in this kind of stuff.

Im just really scared to go back because a lot of the people she knows will be on her side due to her manipulative nature and how she could keep my sisters, dad, nieces nephews away from me for calling her out

So AITAH for finally standing up to my oldest bully despite the fact I could possibly lose my dad and my other family or should I just apologize and try to mediate to keep the peace and keep in contact with my family?

I may have left some stuff out because I’m stressed/in a rush but I will update/comment with what I forgot if I remember