On 16 September 1935, she married the Conservative politician Duncan Sandys (later life peer Lord Duncan-Sandys).

[4][5] With Duncan Sandys she had three children: Churchill was an officer in the Women's Royal Naval Service during World War II.

In 1962, she began working with the Samaritans, an organisation created for the prevention of suicide.

[8] On 20 October 1963, she died at 58 Chester Row, Westminster, S.W.1, leaving an estate valued at £59,259.

[8] She is buried with her parents (who both outlived her) and her siblings (Marigold originally was interred in a tomb at Kensal Green Cemetery in London, but her remains were relocated in 2019 to join the rest of her family) at St Martin's Church, Bladon, near Woodstock, Oxfordshire.