Toxic relationship with mother

Hi, so basically I live at home with my mum, and two sisters. Mum and I don’t have the greatest relationship due to her alcohol addiction and mental health struggles. Both of my younger siblings are autistic. The youngest is 14 and she is on the severe end of the spectrum. She is non- verbal and displays aggressive challenging behaviours. A lot is expected of me at home, despite being a full time student and also working. Basically yesterday I was at work 11-8 as I came home I noticed my sister had badly cut her hair (this is not the first time) I informed my mum as she clearly had not been supervising my sister who needs constant care and attention. It turns out my sibling had access to my room whilst I was at work and had completely cut her fringe off. The scissors used where from my room but where very well hidden so she must of had access to my room for a prolonged period of time to find them. Anyway, my mum constantly likes to blame things on me and can’t take the blame for herself. In fact my mum is often quite negative and verbally abusive towards me which is so draining and negatively affects my own mental health and well-being. This hair cutting scenario has caused a major conflict between us. I understand she is angry that my sister ruined her hair, but do I really need to beg for forgiveness for something that happened that was out of my control. In times of conflict I always try to remain calm, and diffuse the situation but my mum is very angry and hot headed, and she will start saying insults which is obviously very distressing. Moving out isn’t an option right now, but just wondering am I in the wrong, what could I do to diffuse the conflict at this time ? I literally never leave the house or socialise with friends and I haven’t been into uni all year as I’m scared to what I’ll come back to. This obviously is no way to live but what can I do in this moment in time to make things more bearable?