BigR ---- I have been in the same scenario , but the otherway round . My son and a girl on drugs.The police were not able to help-- she was using but not dealing.I tried reason with my son , shouting , crying all to no avail.
So I decided to operate on a charm offensive. I made her welcome in my home , having made sure that anything of value was locked away before she came.I provided meals which she wouldn't eat,washing and bathing facilities which she did use.
I would not allow her to stay over in my house because I felt I couldn't keep watching her 24/7.
So they came and went as they felt.
It was very difficult indeed for me to have a pasted on smile and friendly greeting all the time.
Eventually my son asked me for money for her to get drugs -- and I refused. He lost his temper and left.
The next day he returned , in a right state , having been beaten up by her brother.
All this was reported to the police ,who were sympathetic, that was it.
Time went by -- over a year or more and gradually my son began staying at our home for longer periods.
I asked no questions --although I wanted to do.
My home was burgled twice , and vandalised once in the intervening year.K