She was the daughter of James Brownlow William Gascoyne-Cecil, 2nd Marquess of Salisbury, and his second wife, the former Lady Mary Catherine Sackville-West.
[1] Her older half-brother, Robert Arthur Talbot Gascoyne-Cecil, 3rd Marquess of Salisbury, was prime minister of the United Kingdom from 1886 to 1892 and again from 1895 to 1902.
She married the future earl on 25 January 1872, a year before he succeeded to his father's titles.
A portrait photograph of the countess, taken during the 1870s by John Watkins, is held by London's National Gallery.
[2] The dowager countess had a London house at 17 Upper Grosvenor Street, but died at "Cuffnells", Lyndhurst, Hampshire, of pneumonia, aged 53.