Background - we've had my parents bring Baby Brother's two DDs to join us at a two bedroom time share near a Disney property twice. The third time, we arranged for a three bedroom suite (teenaged son and two girls with the older one in her teens) plus our married DD and her family were joining us as well as Grandma & Grandpa (ten people total - youngest about eight months old).
Last minute to change plans without taking a financial hit passed and THEN we were told that the girls had basketball camp starting the middle of the week, too late to change dates (even if we could, as the dates are arranged around VorGuy's work schedule) and too late to change back to our two bedroom unit.
Last week, BB's wife (SIL) started a conversation about how great it must be to have the time share there and how much they'd like to see it (and stay with us) sometime. I told her that we always vacation in July due to VorGuy's work schedule.
She started to tell me that that didn't work for them and apparently thought that she was going to convince me to invite them to come down this summer....
We were called to the table and I took the opportunity to clearly let her, my brother, my spouse, and anyone else (witnesses) know that we vacation ONLY in July and the first week in August right now until VorGuy retires. No other times will work as long as he has his current job. She tried to start in on how June was just a better time for vacations....and then people started interrupting her to ask her to pass this or that platter or bowl.
I don't know what to do if she brings it up again - it will be summer of 2016 before we can start changing months - and our five year old (by then) grandson will be ahead of my brother, his wife, and two young women of 15 and 17 (or so) on the list of fun people to go to Disney with.
There is a background - but if I post it all here - it will be rather too obvious who she is.
We get along - but if she wasn't married to one of my siblings...we wouldn't be running in the same social circles at all.