Dear Mary — The e-cigarette party is the new Tupperware party

Q. One of my oldest and best friends, who has lived up north for years, begged me to let her daughter move in with us as a paying guest for her second year of university in London. The daughter was literally homeless and staying in a Premier Inn. She promised the girl would be good and would not bring friends back. This has turned out to be true. Unfortunately, we had no idea that her classes would only occupy her for two days a week and that the rest of the time she would be present in our flat. How can we ask her not to be at home so much without making her feel uncomfortable or unwanted?
— Name and address withheld

A. Buy in polystyrene cups and leave columns of them next to a kettle in your drawing room. Tell the girl that you and your husband have offered to host meetings for a certain addiction group on two afternoons a week — which happen to be on days when she is not in class and would normally be at home.