Born Nancy SHARP in Truro, she attended the Slade School of Art, where she met her first husband, William Coldstream, with whom she had two daughters. In the late 1930s she had an affair with Louis MacNeice, illustrating two of his books and partially inspiring Autumn Journal.

During the Second World War she worked as an ambulance driver, and married Michael Spender, brother of the poet Stephen Spender. Their son Philip was born in 1943.  Michael was killed during the last week of the war, and Nancy never remarried. She worked as an art teacher after the war.