Wow! I’m impressed. If I knew this little trick I would have resorted to it many a time. Guaranteed way of making guests leave earlier. Had the same problem with houseguests, played around with the washing machine dial and the cooker, but mummy never said anything to her little darlings. If I said anything I would just get a lecture, “a young child doesn’t understand these things, so don’t try to make them”.
There is a similar breed of Aunty in our area. We have to keep an eye on her whenever she is over, looks in all cabinets, wardrobes, fridges she can get her hands on when the host is out of the room. God help you if she uses the upstairs bathroom, half an hour later she can be found snooping in one of the bedrooms. When asked “Oh, I just wanted to see how much space you had in here”. BS!