Henrietta Blanche Ogilvy was the daughter of the 5th Earl of Airlie. She married Sir Henry Hozier in 1878 but was later divorced. Her daughter Clementine married Winston Churchill in 1908.
She appears to have been quite friendly with JW, and is referred to in JW's correspondence about 1899-1900.
Debrett's Peerage, Baronetage and Knightage, London, 1907; Who was who: a companion to Who's who, London, 1920 et seq; Hardwick, Joan, Clementine Churchill: The Private Life of a Public Person, London, 1997.