[TalnSG]

I think Nyororin is right. This sounds like a classic case of an elderly family member needing to feel useful. Without some concrete way of contributing to the whole, she is feeling distanced from everyone. It crosses all cultures that I can think of.

Maybe you could start planning for a small dessert course - even if only fruit. Have Obaasan help your wife plate the dishes in the kitchen while the kids do their chore of cleaning the table from the main meal. That way Obaasan will be busy while the kids do as they are expected to and she performing a task that contributes to everyone. And if there is also an element of her trying to seem like the "good guy" to the kids, the dessert will satisfy that too.

Simple things like that can make a difference.