Keiller was born on 10 August 1908 in North Berwick during a golf trip by her parents, Daisy Muriel Hoare and J. Wadsworth Ritchie, a rancher. She grew up in Texas.

She married Charles Style, and, as Gabrielle Style, won several golf tournaments in the 1930s and 40s.

During World War II she served as an ambulance driver.

She divorced Charles Style in 1950 and married archaeologist Alexander Keiller in 1951. She was widowed in 1955.

She collected Dada and surrealist art. On her death, she bequeathed a collection of 136 paintings, sculptures, prints and drawings to the Scottish National Gallery of Modern Art.