Yes that was abuse, and inexcusable.
In my opinion she didn’t deserve to be a mother.
It may be worth looking into the scapegoat theory. I’m only suggesting this from the fact that she treated your sister in a completely different way to you.
I have had a very similar experience as my father was a malignant narcissist.
If you are curious to delve deeper then yes, check out info online about the scapegoat child.
Sorry for what you’ve been through and well done for getting this far,
FF