Well, maybe there's more than one thing but LOL
She doesn't have anything fun for the kids to do. NEVER. not.even.crayons!! since they were born, no rattles, nothing. I don't expect her to go crazy buying things for my kids but when I am a grandma I would at least have coloring books and crayons. I always go to her house prepared though, crafts for the kids to do, etc. It's not like she doesn't have the money cause they do. Vent over
OMG, my biggest pet peeve about my in-laws! My SIL used to live at the beach and she would invite us to stay with her for a week every summer. Which was great, don't get me wrong. It's the beach, after all. But SIL completely missed the boat on child entertainment. She never had so much as a coloring book for them. So every trip I packed a big box with craft materials, scissors, glue, markers, paper, etc, and library books. SIL was amazed and she couldn't understand WHY

She really thought the kids could stay busy at the beach 14 hours a day for 7 days. (What, are you crazy? I can't have the kids outall day in the bald bare sun in Florida) She makes no attempt to interact with the kids, play games or do projects. Children are better seen than heard.
SIL is shallow and honestly, she is clueless. When we're down there she only has eyes for her brother(DH) and the rest of us could just go suck eggs, especially Christian. She her and her husband walk around after him smoothing out his footprints in the carpet, wiping up any counter that he accidently touched, literally following him from room to room to make sure he doesn't touch something. That's why I put my foot down. Enough of it. It's bad enough that they can't even hug Christian, but they have made NO effort to get to know my older kids. Therefore, my kids could care less about having a relationship with them.
Recently, DS24 went down with my DH to visit his Sister and Mother. DS has long hair,two lip rings, and wears a lot of black. He's a decent person, well-read and well-spoken. He writes music & graphic novels, and he takes care of his younger sibs . DSil was horrified by his "look"and told him he was going to hell. Then when he got home she sent him a Christian self-improvement book.
And Dsil wonders why we don't stay with them anymore...