Addicted 6 yo sister

I have a 6 yo sister, she has a tab of her own and is chronically addicted to it (6 hours of screentime). Not only that, her friends at school arent much of help. Idk how but I've seen her being colorist/racist alot of times. We were at a restaurant one day and there was this kid whose skin was darker, and she literally said "Mai to isse kabhi shaadi nhi krungi" (I will never marry him). Obviously I was shook, wondering how she even thought about that. I asked her why, she said "Ye to bohot kaala hai" (He is very black). I believe her thinking is shaped this way because of the internet and of the influence of the kids at her school. She doesnt know how to talk to elders. She has said "agar aapne baat nhi maani toh mai marungi" to me, and my mom... she eats candies every day and has recently got diagnosed with metabolic syndrome. I've told my parents alot of times to take her tab away and not give her candies, but they dont listen to me. Even after getting diagnosed, my father still gives her junk food. I got so mad that I shout at him and still feel guilty for that. But tbh the environment at our home isnt that pleasant as well. My sister has been exposed to abuse almost everyday in her life. My father and mom fight like once a weeks and my mom hits my father with a broom, bottle, cuts him with her nails and whatnot. my sister always cries and gets hurt in the process. I've told her to not get involved as I've learnt my lesson and become numb and dont even get sad when they fight, but she always does and gets hurt in the process. Kids at school ended up eating her lunch once. IDK what to do so pls give some advice