I have had a horrendous experience too! Let me tell all! I too am a kind, generous thoughtful guest so the thought others aren't is truly shocking isn't it?
DH used to pay for sil's flights to come and see us because she desperately wanted to see her baby nieces. She arrived, wanted to buy them expensive gifts so I took her to a boutique shop, she announced she hadn't brought her purse at the til, I ended up paying for them!
As I worked and had 3 under 3s, we had an au pair. Sil slept in til noon everyday and screamed abuse at the au pair when she accidently woke her up doing the vacuuming.
Oneday sil announced she'd 'give me a break' and play with dc, she lasted 20 mins then announced she was tired and was going back to her room to quietly read a book!
I fed her 3 meals a day, she did nothing to help, just read and sauntered through the gardens.
I was heavily pregnant, exhausted from keeping everything 'lovely' for sil's 2 week visit. I had the electric hedge clippers and was on a ladder resting against row of plum trees I was in the middle of doing. She was lying on a blanket on the grass and said 'Could you make me a Pimms when you're done?'
The last straw was when she called me into the lounge, she had, without my permission, altered the layout of the room and took away throws etc and proceeded to lecture me on how I could make even more improvements.
There! Confessed! (By the way Mugville here listened carefully to her suggestions and had her to stay at least for one other extended visit before Endof.)