>>Just what I was thinking.<<
Just what we do.
I don’t want my daughter to go through it again.
I think even very small children can understand that other people are not always any more perfect than the child is.
And, that when grandma is forgetful or thoughtless or whatever, that the child can count on me the parent to make up for it as best I can. And that will have to be sufficient.
They must forgive granny and also not get stuck in resentment over it.