Mary began writing with in her teens. She wrote in her journal in 1877, "What a pleasure and interest it would be to me in life to write books. I must strike out a line of some kind, and if I do not marry (for at best that is hardly likely, as I possess neither beauty nor charms) I should want some definite occupation, besides the home duties."
Mary began by publishing some stories in The Graphic and her first novel ‘The Danvers Jewels’ a detective story followed in 1887. It was followed by Sir Charles Danvers (1889), Diana Tempest (1893).
After her father retired in 1896, she moved with him and her sister Diana to Condover Hall before selling it to move to Albert Gate Mansions in Knightsbridge, London.
Mary wrote the best seller ‘Red Pottage’ in 1899. It satirised religious hypocrisy and the conceit of country life. It was denounced as immoral. It also explored female sexuality.
During the war she did clerical work in the Carlton House Terrace Hospital. The sisters moved in
1919 to 4 Argyll Road, Kensington, where Mary died, unmarried, on 15th July 1925.