Khaman
Headed for rehab.
How did you find out it was your sister’s friend? Who is the “legal” head of the household? If it is you then I would notify the police that she is persona non grata in your home so that the next she is near your home you can file trespassing charges against her. I would also think that lots of furry dead animals need to find their way on to her porch, if not her bed.
What does your sister have to say about her "friend's" actions.
What does your sister have to say about her "friend's" actions.