What she is doing is what I call "Playing the guilt card"...she is working on your emotions and good nature. Trying to make you feel guilty for having what she wants...not needs. She needs some serious counseling. Try not being home next time she knocks. Get a key and lock the door if necessary. I know how hard it is to say NO but for the sake of all of you ...try it. I feel sorry for your DIL...no child should have to explain away their parents bad behavior. If she does this with other people , sooner or later someone will accuse her of stealing something that may go missing.