She married him. This is her article from thepeerage: "Lady Alexandra Louise Elizabeth Acheson1 F, #85022, b. 1878, d. 21 January 1958 Consanguinity Index=1.56%
Lady Alexandra Louise Elizabeth Acheson was born in 1878. She married Lt.-Col. Hon. Frederick William Stanley, son of Frederick Arthur Stanley, 16th Earl of Derby and Lady Constance Villiers, on 17 June 1905.1 She died on 21 January 1958.
She was the daughter of Archibald Brabazon Sparrow Acheson, 4th Earl of Gosford and Lady Louisa Augusta Beatrice Montagu. Her married name became Stanley.
Children of Lady Alexandra Louise Elizabeth Acheson and Lt.-Col. Hon. Frederick William Stanley
Major David William Stanley+ b. 9 Aug 1906, d. 14 Jan 1997
Olivia Mary Beatrice Stanley b. 1 Jan 1908, d. 9 Jul 1985
Diana Margaret Stanley b. 18 Feb 1909."
Lightness added to bring out details of coiffure and hat by gogm.