Background:
My SIL is a piece of work, I think she comes inches from neglecting her children. She is married to my brother - who has a full time demanding job with travel. He knows there are issues - but he is not willing/wanting to deal with it. My mother has tried ..... but to no avail. During the day - there is no schedule, meals are usually fast food or snacks. SIL does very little cooking. Niece has nice clothes, pool and tons of the latest toys - but very little time and attention from her mother. ( For example - her hair is always ratty and not combed. I spent an hour combing out the snarls and then braiding nicely. She wore it that way for 2 days. SIL was too busy to take it out and redo it. )
Niece ( Emily ) is 8 1/2 - but is in many ways immature. Both my brother and SIL do not believe in telling children no.

She has learned to get what she wants by manipulation / whining etc. She can be a real sweetie and wetry to spend time with her when we can.
end BG
We visit my family 2 times a year and stay for about a week each time. I try to divide up my time with my various nephews and nieces so that we get one on one time with them as well as big family time with all the cousins together. We picke up Emily and took her with our 2 boys and my parents to the lake to swim. We had her all day and took her out ot dinner with us. We had an absolute blast. However after dinner - when her Dad was going to pick her up - she started with she wanted to sleep at grandma's ( my Mom ) we both told her no - that we had to get up early the next day and the house was full. She then kept saying she wanted to come over and see us all day the next day.
I told her it wasn't possible ( we had plans with other brother and his family - which I did not mention ) but we would see her on Wednesday. She started whining / pouting which I ignored.
10:00 pm that night - my brother called - she had been crying for 2 hours because she wanted to spend the night at grandmas and she wanted to see us the next day. He told me " She can't believe that AUNTIE POF and Grandma told her they didn't want to see her".
I told him that we had spent the ENTIRE day with her - but our plans they next day were with some older nephews and nieces. he aksed - well why can't I drop her off ? I explained it wasn't possible. he asked - well can she come over and say goodnight. ( by now it was 10:30 pm ) I said that wasn't a good idea - we were going to bed soon. He mentioned - well she is really upset - you talk to her. So I did and I told her that no she could not come over and that we would see her on Wednesday.
I feel sorry for her - she has fun with us and gets lots of attention from DH and I - but at 8 1/2 I think crying over it to that extent was a bit much. I was very annoyed at brother since if he had been firm with her - I think she would have gotten over it sooner.
The phrase did work - and the other thing I learned here was not to explain and not to mention other plans. There was no wriggle room.
The sad thing is that we were really considering surprising her with going to Disney with us this winter. She has a sibling with special needs - so even if they go - pretty much her parents are focused on sibling. ( Well my brother is - SIL is pretty much focused on herself ). But this was not the only example of whining / crying / not accepting no . We had to make a quick stop at the mall to pick up a prescription and she pretty kept on and on and on about me buying her a book. ( I had given her a nice present the day before ). She did everything she could to talk us into it - even after a firm no. She was pretty much that way all week and DH said - NOPE..... not dealing with it on a trip. ( Especially when my boys have been taught better ).