Does she have enough "structure"/rules? It doesn't sound like anyone is paying "enough" attention to what she's up to? Is it just she and your aunt? Is your aunt up to the job of parenting a difficult teen?

I would get help for whoever is parenting her, how to deal with someone with her background and problems. Perhaps her doc can recommend someone?

http://psychologytoday.com/articles/...06-000003.html

http://books.google.com/books?id=AEJcHjY56bUC