my sister has body image issues because my mother makes her think she's fat and disgusting because she's a little chubby and has some stretch marks on her thighs. she's 12 years old

what do I do. she's done it to me, and I trying to defend my sister. but I'm seem to make it worse by standing up to her. my dad won't do anything

and my mother thretended to kick me out in a month for defending her. I'm 19.

she collapsed in my arms. I broke down crying with her. she shouldn't care about body image but it affects her so much more than it should any little kid.

I don't know what to do...

edit: my mom said I was breaking this family appart. that I was a cancer and I was eating and manipulating this family. I can't report her. I don't think anything would be done. I'd cause more harm and I'd get myself kicked out sooner. I'm in nursing school and I can't find a job because of how young I am. I need this home. I feel helpless.