Question: When did Lady Dorothy Macmillan's mother die?
Sentence (from "Lady Dorothy Macmillan"): Lady Dorothy Evelyn Macmillan (28 July 1900 – 21 May 1966) was the third daughter of Victor Cavendish, 9th Duke of Devonshire, and Evelyn Cavendish, Duchess of Devonshire.
Relevant evidence: Yes