For somebody who grew up with dogs and had them all her life she certainly should know better than to walk a dog without a leash. Isn't the park at Windsor Castle big enough to exercise a dog that she had to go where there were other people around and put them in danger?
You may not remember this but, many years ago there was an episode in "Monty Python Flying Circus" that had to do with "Her Royal Highness the Dummy Princess Margaret." She is not around anymore but it seems to run in the family.