B.M.
Why is she stealing? Does she want the "stuff" or does she want the attention?
Have you talked to her and asked her why she does this?
First I would stop letting her go to other houses. Interacting with friends is a privilege, not a right. So, until she understands how to behave in society, she can't go. Period.
2nd - she needs to be supervised more heavily. Like constantly. Don't give her any chance to steal from you.