my sister's words making me feel bad about myself/insecure

I don't even know where to begin. My younger sister has been rude to me for a long time now. She has made fun of my looks, the body, the way I dress, the college I go to and my friends. For example, on many occasions she has said that all my friends are ugly. She makes fun of the college I go to and says that I am a failure, will get nowhere in life and have to live with my parents because the school I go to isn't "prestigious" in her opinion. She compares me to influencers who are my age. She would show me pictures of influencers my age and say things such as "Oh she's so much prettier and successful than you. You are doing nothing". She always says she is prettier than me and that she "mogs" me. I have always had scars on my legs, and I have been visiting the dermatologist for this. My sister says hurtful things such as "Ohh eww what are those things on your legs?? I do not have any, see my legs are clear. Maybe if you shower they will go away". What she said has made me so insecure that I have not been able to wear shorts or a dress this entire summer. Last year, I went to a concert and before I went to the concert she saw my outfit and gave me the most disgusting look and said "Ohhh...that's what you're wearing??". This ruined my entire mood and I was upset during the concert. I am really frustrated and I do not know what to do. I have told my mom about all this but it is not doing anything. All these things she says just makes me feel so bad. I am not sure how to navigate this situation, so I am looking for advice. Thank you.