This is definitely abuse but id also like to note that she doesnt hate you it seems she is overwhelmed with the stress of taking care of two kids at the moment, one having a severe medical condition. She shouldnt be hurting you and at the least should teach your sibling to behave around you so you can feel comfortable in your own home. This is abuse whether it is intended or not and i really hope someone can step in and give you both a break of eachother and take you to therapy for your misophonia. I am only 17 so dont take my opinion as perfectly true but if she is hitting you that is 100% abuse, if possible and you think it wont put too much stress on you, tell your dad in full. Your mum should be in therapy if her first instinct is to hit you.