A distant relative once came to stay with us - they live abroad and she was doing a tour of Europe. She was supposed to stay with some other relations (arranged about a year in advance) but unexpected and sad circumstances intervened and they were unable to accommodate her with just two days notice - so following a desperate begging email we offered to step in rather than leave her thousands of miles from home with no accommodation.
DH and I both work full time and this was the week before Christmas - neither of us could organise extra time off as we had a holiday booked over Christmas week so we said she was welcome to stay but would have to amuse herself / chill out at ours while we worked and DCs were at school.
To say she was unappreciative of our efforts would be a huge understatement, she also turned out to be the most awkward person I have ever met in my life.
Nothing I cooked that week was acceptable - even though after the first night of her refusing dinner I asked what she did like so she could be fed. Even after shopping especially for her and cooking different food to suit she still ate sod all. When offered a glass of wine she accepted and then "didn't like" red, white, rose or fizzy - what the hell else is there ? 
She wouldn't join in family evening time and went to bed straight after sitting at the dining table and grumbling about the food every night.
He room was too hot, then too cold, then the bed wasn't comfortable, so we moved her to another room and shuffled the DCs around - she still wasn't happy as that room was too quiet and she still couldn't sleep.
We bought Christmas presents for her to take home for herself, her DH and her DCs and when she'd left we found them under the bed opened and obviously deemed unacceptable. She also put Christmas cards that DD1 had lovingly made at school for her and her family in the bin - nice eh ? 
I did manage to swing a half day from work and took her out for lunch and to see to a very famous University City - she "didn't get" the point of the city and complained about the service and (yet again) the food in the restaurant (personally I thought it was excellent).
She moaned about me disturbing her when I was packing for us to go away on holiday, we were due to leave the day she was going so it was a job I had no choice about.
Finally when we came home from our holiday she had sent us a postcard from the airport saying how she thought we were bad parents for both working and using childcare for our youngest DD and that she wished our children luck as they would need it 
I'm sure there was much more that I've missed here but my memory has selectively blocked it out 
Thankfully she unfriended both DH and I on Facebook soon after her visit and we've never heard from her since.
Absolutely the last time we offer anyone we dont already know well housespace in an emergency 