To wish people would make plans with me not my 7 year old

[Roopdedoop]

Booked a days holiday from work to spend with my DD because school is closed. MIL picks her up from school sometimes and asked her if she wanted to spend the afternoon with her on the school closure day as she’s picking cousin up that day. So she’ll be taking her from 1.30. They didn’t tell the cousin in case it was a no, so he wouldn’t be disappointed; but because they asked my DD if I say no she will be disappointed. She came back from MILs all excited to be going to see her cousin. I’ve said she can go obviously as it’s not her fault. I know it’s not the end of the world and I can relax for the afternoon, I just feel a bit sad because I booked it off to spend time with her.

Am I being unreasonable that it should have been run past me before asking me DD?

YANBU my mum does this and I will explain to my child in front of her that we already have plans and granny should have spoken to mummy first etc.

You tell MIL 'no, we have other plans'.
MIL won't learn to ask you if you cancel your plans.

Not intending to have drip fed but I also have a badly sprained ankle so I can’t do anything exciting with DD, but had just planned a cosy day with her and we were going to do drawing, painting, colouring, maybe some baking etc.
So on this occasion I’ll let her go but I just think it should have been me that was asked and not her, also feel like I’ve been narky this morning and conscious I don’t want to take it out on DD either!