Mutznutz, I agree with you on this one. I've had dealings with physically abusive teens in the past.
I would wait until a calm moment appeared tomorrow and then explain why its not ok to hit people - especially your mum. If there is a mark, in some ways even better, show it to her and make her feel bad about what she has done, explaining THAT is why she doesn't have her mobile etc.
(Different things work for different people, but this is what my partner and I did with a friends teens when she couldn't cope any more and we were left with 2 scary teens for a fortnight and it did work.)
Next I would write out a list of "expectations" What she can expect of you and what you expect from her. And stick it on the wall.
ie,
you, cook dinner, clean the house, pay for food, You collect her from school, you take her to places,etc
She, Keeps her room tidy, brings her washing to the machine, gets up when asked, goes to bed by ( whatever time) speaks to you as she wants to be spoken to.
If she helps with certain chores ( washing up / hoovering etc) then she can get extra priveledges. ( extra screen time / top ups/ whatever)
Both of you have to show respect for each other, and you need to find an activity to do together even if it means feigning an interest in some shite group or game that she likes to play, shopping, watching funnies on youtube, anything because you need to keep the bond between you going, otherwise she will cease to care whether you are dissapointed in her or not. At that point it will get much more difficult to pull her back.
I'm dreading the teen years with my own kids, hope you are ok.