Terry Pratchett has written many forceful, nay, overbearing female characters who can sometimes cow even rugged Watchmen and powerful Wizards: Mrs. Whitlow, Mrs. Cake, Mrs. Arcanum, Miss Maccalariat, the stereotype of the domineering British matron spans the Multiverse from Bertie Wooster's Aunt Agatha to the Discworld. Usually these have redeeming qualities and hidden weaknesses which render them more human and understandable, but like Shakespeare's Iago or Discworld's Carcer or Teatime, the rare monster can turn up. Consider Ermintrude Fanshaw's grandmother, who has no given name, nor any other trace of humanity, only a character like an iron bollard.
Grandmother's powerful sense of right (very little) and wrong (lots) obliges everyone in the vicinity to bow to her will. She will defer to the King himself, although her loyalty fails when His Majesty sends her son as Governor to the other side of the world and out of her control. Her patriotism, like the rest of her morality, is subject to her self-absorption.
When her son becomes king, he appoints her Ambassadress to The ReUnited States. We haven't learned what the American federation did to annoy him.