That is very close to child abuse. If you start to get and marks or bruises or stuff like this continues, then you should either call 911 or better 800-799-7233.
Also, when she is calm, try to see if there is anything going on in her life that is hard right now.
Friendly reminder that id you call the police or that other number I gave you, your mom could be arrested and you will either go to foster care, or live with someone else in your family.
Not trying to scare you or anything, just want to help you understand.