Ok, no child deserves that treatment whether it is from an adult or another child.
I was one of three growing up and the fights I had with my brother, and the fights I had with my sister were very different. Up until my sister was 16 we had sibling rivalry fights. Hair pulling, name calling, fighting over toys.
Me and my brother on the other hand, that was much different. Even though he was 3 years younger than me he broke my nose with a children's bible, he locked me out of the house. He blamed me for stuff that wasn't me knowing I would get a beating from my mother. He hid food under my bed and tell my mother I stole it and watch me get beaten. That was abusive.
I would say your sister was abusive. You as not making a big deal of it, whether she was ill or not doesn't give her the right to treat you that way.
This is just my opinion coming from a messed up family, but do you think it might have been a case of your mum placicating your sister as not to endure another flare up?
My grandad knew my mother beat me but said nothing for a quiet life. He was scared of her, and still is. Not that she would hurt him, but she would make his life hell even if he phoned me.



You did nothing wrong

Hang in there