What happened to the duchess of windsor after the duke of windsor passed away?

Answer 1

The wife of a Duke remains a Duchess for the rest of her life

Thus, in the case of Wallace Warfield, she was "Her Highness, the Duchess of Windsor"once she married Edward (the Dukedom having been bestowed upon her husband (formerly King Edward VIII of Great Britain) by the ruling sovereign, his younger brother, George VI). Edward had, by birth, the pre-title "His Royal Highness"; during his brief Kingship, this pre-title was changed to "His Majesty". Upon abdication, King George VI, by Royal prerogative, gave the abdicated King the total title of "His Royal Highness, the Duke of Windsor" (Windsor has been the name of the Royal House of Great Britain since World War I, when it was changed from the German "Hanover"). When she married him, Wallace Warfield became "Her Highness, the Duchess of Windsor". Only by decree of the ruling sovereign can one be declared (or cease) to be "Royal".

So, when she married Edward, the Duke of Windsor, she was thereafter properly addressed as "Her Highness, the Duchess of Windsor", and he as "His Royal Highness, the Duke of York"; and these titles each individually carried to the end of their respective days.

Titles in Royalty are basically surnames (or last names). Therefore, when Wallace Warfield married Edward, the Duke of Windsor, she became Wallace, the Duchess of Windsor (or in American terms, he became Edward Windsor, and she was "Wallace Windsor".)