I DONT KNOW WHAT TO DO😭

My cousin lives on my street and goes to my school! We used to be best friends but now we have a lot of tention. I try everything i can to be nice and have a healthy relationship with her. However I’m shy and she’s not, she always teams up with ppl and says rude things to me. She makes my school day and life miserable by saying i have a ugly bf, saying i have no ass and just rude things that get to me. Also all my cousins chose her over me and at ever event i get left out:( she also has a need to want to ruin my relationship by involving her life(drugs and alcohol) and my bf hates that stuff! She always pressures me into doing it and giving my bf sexual things even tho I’m not ready. When i say no she makes me feel bad. I don’t know how to stand up to her bc tbh bc I’m so shy, she controls me:( i need help