AITA- For not wanting to come to terms with my mother’s husband after a serious argument

I (17 F) am the eldest sibling of my household, the only girl and my siblings are spaced out by a few years. There’s 4 of us in total and 3 of us have medical/mental issues (this will come to play later in events).

For context, I have a good relationship with my mother. As of recently, my mother is married, no wedding, nobody knew til she showed the certificate. Not that I have a problem with her being married or being in a relationship, though I think she should’ve thought better of who she’s marrying. Shortly before they had gotten married, there been a few disagreements I had with him. But I kept it civil and still respected him because that’s how I was raised.

This happens 2-3 weeks after my birthday in the beginning of December, I had been sitting in the kitchen listening to music when he had came through the front door and headed back towards the bedrooms. I didn’t think much of it and continued listening to music until my music stopped and I heard my brother yelling. I got up and headed out the kitchen, through the hallway I saw my mother already at the door of my brothers room along with her husband (Mike). My mother and Mike were in the doorway and my brother was still yelling, he has autism on a high spectrum. So I came closer to try and ask my mother what was going on and possibly comfort my brother. Before I could ask Mike muttered something like “Here she comes acting like she‘s backup.” So I turned before in general asking what’s going on. He caught an attitude or whatever before he had walked into my brother’s room and yelled at him to stop screaming. That scared my brother badly and I said “Don’t you yell at him like that and you out of turn for that.” Then me and him were going back and forth yelling at each other, my mother tried forcing me out into my room. And I refused, he was yelling about how I was tryna act grown and I needed to get a job since I wanted to be so grown. That’s when it amped up and more screaming is happening while my mother tried defusing the situation but it keep going as I kept yelling that he shouldn’t be yelling at my brother like that and how she was letting him yell at me any kinda way. He’s cussing and stuff while I’m trying to not cuss him out in front of my mother, then he was talking about how disrespectful I am and how I never listen to her, how he’s ready to go and she need to help him leave. When my mother finally gets me in my room, I was crying and left alone. After that he stormed out and my mother sat with my brothers. The situation finally defuses after he leaves and my mother sends him on his way. Before that he apologized to her and told her to tell me his apology.

More than a month later and I still don’t accept his apology, nor do I care for him or any of his problems. Now my mother tells me “I eventually need to work it out with him”. AITA For not wanting to?