in my experience (well little experience) what i have found is the story of the bully from bridge to terabithia.
dd loves that child, of course an older child but i dont like the child's behaviour.
what has helped, always, always, always - is me putting up huge boundaries around my place. not as punishing, but more as expectations.
they have tried to break them, get around them, but i've been pretty firm.
and slowly but surely they somewhat come around. some of them we strike a balance.
some of them as they grow up enjoy being at our place and would actually end up hanging out with me helping me with chores.
in almost every single case they either had a sad homelife. either no one home or if they were home they were in TV land after working a lot.
only have i had a problem with one kid with whom even dd wanted to cut off contact. seh was a much older girl and she had special needs. it wasnt so much the girl but that dd had a hard time at her age dealing with her.