I've spoke to Mum. She's not happy
Not happy with you? Not happy with DD?
You have just scuppered her 7 days of child-free week. (At £300 spending money for the child I think she could have paid for a Summer Club or something - so I don't think money is the issue.) But 7 free nights without parental duties is not to be sniffed at!
I looked after DN almost every weekend after my DB died. I wanted SIL to build a new life for herself (like me, she was a young widow). But one weekend - this week 5 years ago - DN 'acted up' and wouldn't engage with my Annual BBQ visitors and wouldn't allow other children to go into the Lazy-spa if he was in there.
Two guests were due to be child-minding themselves that weekend, and chose to collect their grandson from 100 miles away and bring him to my Annual BBQ which was a mix of child-focus and adult-focus.
ME: DN, let the other boys come into the hot spa with you
DN: They splash me
ME: You have your goggles here, put them on
DN: Then I can't see when they splash me
ME: But you splash with A and W when you play in there
DN: I don't feel like splashing today
ME: Well, would you like to come and sit with me and Uncle F?
DN: You're telling stories when I wasn't there. It's boring
ME: Are you ready for a burger?
DN: Don't like them - not the same as my DM buys
ME: There are sausages or frankfurters... you have both at my house before
DN: I don't eat them now
ME: I have home-made Margueritta Pizza - you like that
DN: I don't like your Pizza, I only like [name of fast food Pizza]
ME: You are not being nice today. You are spoiling R's Annual BBQ. Come for a walk with me away from everyone else and tell me what is bothering you.
DN: I walked with you and R earlier, I am not walking again.
I gave him a choice - either join in and share OR phone DM and say he needed to be collected immediately. DN decided that he would phone his DM to be collected immediately.
90 minutes later, my SIL arrived in my back garden and I said 'hello - J's in his room and won't join in'. She picked up DN's weekend bag, and spoke to one of my guests to say "I am taking him home. He is very bored. SW doesn't have an x-box and that is what he likes to play with."
I simply will NOT be controlled by a child's bad behaviour.