Would SIL provide drugs if the mother was a drug addict?  Why she thinks it's okay to enable her is beyond me.  Not only has she inconvenienced people, she's committed a crime!  Say no and mean it.  Ask your husband the question I asked to help him put it into the proper perspective.  Oh, and make sure you are signed up with some credit fraud service.  They let you know right away if someone has opened an account in your name.