Nannan2
Exhausted- maybe your mum thought your daughter will just be rebooking for another day then,as usual, and will pay her then when its done?
That's not how I read it.
I read it as "My daughter has a fixed day each week she goes there. She can't do that day - mother has had to accept that. She can't do any other day that week either".
Maybe illness is the problem - but something that means it can't be rescheduled during the few days either side.
Got the distinct impression that grandmother will make excuses to suit herself for not paying until the cows come home. Lots of people tell themselves what they want to hear - even when it ain't so - and my suspicion is Gran is one of them.