I think the longer time passes, the 'Diana Factor' lessens.
... exactly so
O-D.
In fact, Camilla
is at the moment Princess of Wales - cos that's what you call the wife of the Prince.
In the same way as O-D's wife would be Mrs O-D,
whether she chooses to call herself that or not!
Personally I think "Countess of Chester" has a nicer ring to it, although of course a junior title to that of a Duchess.