Question: What is the date of death of Harriet Leveson-Gower, Countess Granville's mother?
Sentence (from "Georgiana Cavendish, Duchess of Devonshire"): Georgiana Cavendish, Duchess of Devonshire ("née" Spencer; ; 7 June 1757 – 30 March 1806), was an English socialite, political organizer, style icon, author, and activist.
Relevant evidence: Yes