I cant stand my older sister what should I do?

So im sorry shes calling you names no one sould undergo mental abuse like that. Im going to ask if there is anywhere you can go for a bit to get a break? if not possibly find a way to fully express what she does/ how she makes you feel to your mam, like voice record her.

My older sister constantly berates me such as calling me names such as fat and ugly. Thing is she only does this to me and no other sibling, I'm always the one receiving her verbal abuse. This morning she said to my little sister "Don't eat too much, I don't want you to be fat like the other one", by 'other one', she meant me. Thing is I know I am big, but I am working on it Im going gym and eating a lot healthier than before, I just hate the fact that she is so quick to judge people, but when the people judge her, she gets angry and defensive. I was angry about the fact that she called me fat, and so I went out and then came back, and I was still angry, my mother complained about why I was being moody, and I said I don't like the way some people in this house are talking about me and she said she has already dealt with it. My mum always does this, she doesn't know how deeply those words affect me she probably just told my sister off lightly, but if I ever said something like that I would be in big trouble. My sister always finds my shortcomings and makes fun of them, there's a difference between teasing and bullying she is a bully. She would never help me out, but if she needs s my help I have to give it to her otherwise she will start shouting at me, I'm tired of this, I know I am going uni this year but still, October is a long way away, and I want to give her a taste of her own medicine.