So, I have a half sister. She's 13. I have a question.?

She's overweight, she's loud, she bullies her friends, and she talks too much. She has this ghetto accent that her lisp makes it sound even more ghetto and white trashy then she would without it. Right now, she's in her room with her door closed scarfing down a king sized bag of cool ranch dorritos in front of her friend who is almost underweight and talking nonstop and loud about events that took place in school, in the school office, in the school hallway, how she hates this stupid little girl and blah blah. I can hear every word she speaks, but not her friend. Her friend is nice, quiet, and polite. Everytime she is home, it's like this. Sometimes I can't bear it and I tell her she is talking too loud or too much, or I just leave. If her friend isn't home she's on the cell phone. What do I do with this? She's so rude.