Been through a fairly traumatic 3 years splitting from her dad who has been totally sporadic with contact. We've moved house schools etc. But she's had good support from extended family and has been generally happy recently.
Until now, she literally will not listen to anything I ask of her, horrific to her middle sister, bullying I would say in words and physically. Backchat, attitude. I've tried one on one time which she blossoms in but then straight back to shitty when she can't get her own way. I talk to and listen to her. I lay down the law and remove things. Nothing works.
Tonight I've lost my shit as she refuses to go to bed and hidden under my bed so I can't get to her. I've removed a treat from tomorrow she just said she didn't care and carried on. I've removed her book and bag she loves. No reaction. So I called her a defiant little shit, said I didn't want anything to do with her and she can do as she pleases and have come outside before I resort to hitting (I don't hit) 
I'm such a twat losing it like that, I know I shouldn't have but I'm so stressed.
Help! How do I get through to her and keep my cool?