[1] Simpson wrote biographies of her father[2][3] and two of her brother Walter's friend,[4][5] Robert Louis Stevenson, one a study of his early life,[6] and one a shorter work, "a flashlight biography, a nutshell appreciation.

"[7] She also wrote a "readable, if not authoritative"[8] book on folklore in Scotland, including the tradition of Beltane, lore about fairies, and fishermen's superstitions.

[9][10] Of her book Nelson and Puck: Dogs of Other Days (1882), one London reviewer predicted that it "will no doubt be duly appreciated by those for whom it is intended, but cannot be of the slightest interest to others.

[12][13][14] Simpson toured as an author in the United States and Canada in 1899, and was described as "a devoted bicyclist" and "animated and witty".

[15] Simpson died from liver cancer on 23 January 1920 at Edinburgh, aged 64 years.