The way I remember it is that even a widowed woman's social name remained
her husband's (Mrs. Homer Simpson, in this case) even tho Homer himself may
have passed on.
It was only if she divorced and kept her married surname that she became
Mrs. Marge Simpson.
These things were much more complicated back then, but the social
conventions were a good way to satisfy our ever-present pre-occupations
about what our neighbors are up to!