My husband got pissed off at me because i slapped his daughter.....advise?

Ok my husband has a 12 year old daughter, she was a product of my husbands ual abuse he endured as a child and well we got custody of her but its been hell. All she dose is undermined me and calls me name's and tells me i am a worthless wife and that i am a ****. And well she think i am harming my husband which i am not he suffers from adhd,PTSD,Epilepsy,Depression and bi-polar. Me and my husband just go married back in March but we have dated/known each other for 12 years. And well she was going off on me last night and i slapped her, and my husband saw this and got very mad and started yelling and cussing at me. I know he is very very protective of her and everything. But i just don't know what to do, Advise?