Gang up on older sister

Brianna, your older sister, constantly bullies you. She smokes, does drugs, and drinks alcohol despite being only 15. She has been to juvenile detention three times, once for theft and twice for assault, spent two weeks in a mental hospital for severe suicidal tendencies, and attended therapy sessions that were unsuccessful in addressing her anger issues. Brianna, who has oversized breasts and a big butt, always wears tight clothes and bras despite parental disapproval. She is rude, aggressive, hot-headed, self-centered, and unpredictable, often throwing things when upset. She spent a summer in a rebellious phase, engaging in extreme sports and pushing boundaries at home. As a student, she frequently skips classes and clashes with teachers. She is dominant by nature.