My only correction would have been that you should have addressed K, not the girls. Saying something to K like "I know you want to show the girls pictures, but if *your daughter* does not eat soon, she will have a hypoglycemic attack" would have been more appropriate than threatening the girls with a punishment. They are simply not old enough yet to be punished for their grandmother's actions; if the grandmother had then ignored you, then the response to the girls would have been, "Mom is going to fall down if she doesn't get something to eat. Please help us keep her from falling down, or we are all going to be really angry and at that point there will have to be punishment."

It sounds like a horribly frustrating situation, and certainly one where it's hard to keep your head. But if K isn't being an adult, the rest of you have to be.

*hugs to all*