The difference between the Late Queen Mother, and the Late Princess, is that one represented all possible hopes fulfilled across many decades, and the other the absolute reverse.
Queen Elizabeth was mourned with restraint and her life appreciated for longevity and happiness, as the Queen herself said in her address before the funeral "this is what my mother would have understood".
Diana was remembered, not it seemed by those closest to her, two families who squabbled over the minutia of flags and protocol, venues and guests - long after the milk was spilt - but by ordinary people who saw only 16 years of public life, not almost eight decades and felt short changed of Diana as much as she was in the end short changed by life itself.
Heffer, again siding tacitly with Charles, fails to see what Diana did other than as beyond the pale in her walk of life, but in the end cooperating in the book was all she had to reverse the destruction of her life at the hands of her husband and his mistress, their friends and PR machine - and even the Establishment which protected the institution, not the players by marriage.
The Queen Mother would have understood women who had a place and a position, and in return ignored their husband's attentions being elsewhere - for this is hardly a new thing in the world she knew or even within the Royal Family. This is what she did not understand about Diana's choice to do otherwise.
Perhaps the Princess of Wales was too modern, too bourgeois, in that she did not accept the role of an aristocratic wife in the breeding department beyond which she was mere set dressing. God knows her own mother bucked at it.
I suspect most modern women, understanding the nature of their marriage from the outset as hollow, have respect for Diana in that. Marital breakdown, divorce, has featured in my own family but Nana, married long before the war, was of the same school as Queen Elizabeth: you do not discuss your marriage; you make your bed and you lie in it. That has been the great change in attitudes since the war years - we should not contrast the two women, as here, for being of generations 60 years apart.