My mum and sister gang up on me?

My mum gave my sister something I've been wanting for years. My sister doesn't let my mum go out and if she does go out my sister will scream and shout, she calls my mum a bitttch, she throws things off of her face, she orders her around. I thought it was so unfair because I always let my mum borrow my money, borrow my clothes, babysit my sister so she can go out. So anyway I was in my bedroom with my friends little brother and my sister comes into my bedroom and i said loudly get out and my sister said no, she then went and told my mum that I was shouting at the baby! I would never shout at a baby! So I pushed her out of the room with my foot and she attacked me grabbing my ear and nippong me making cuts on my ear and my

Mum slapped me across the head five times. I am not letting this go because I am tired of the way my sister acts and my mum just lets her do it! I now have to lie in bed because I don't want to see them today. I feel like crap..... What would you do?