It was a bad time to choose to visit especially if your MiL was planning a special last meal. Although my house is always open to unexpected visitors I would have been rather put out myself, mainly because the meal might not have stretched to another 4 (?) people.
That said, your MiL could have been more tactful and handled the situation better. I'd have asked you to come back in a couple of hours saying that we were just about to eat but would love to see you then.
Fascinating causes of death 1632


I suppose it's true that there's nowt so queer as folk!