Blow trained at St Martin's School of Art from 1941-1946, the Royal Academy 1946 -1947. Although formatively trained as a figurative artist, she converted to pure abstraction in 1947 after meeting the Italian artist Alberto Burri at the Accademia di Belle Arti in Rome.
Being an abstract artist in the fifties was radical, being a female artist working in an abstract idiom even more so. Despite this Blow secured her first solo exhibition at Gimpel Fils Gallery. A further solo show followed in New York in the same year. Aside from annual summer exhibitions at the Royal Academy in 1958, she won an International Guggenheim award and was represented at the Venice Biennale.
In 1957 Blow visited Cornwall and subsequently re-located from London for a year where she stayed near to her friend Patrick Heron. After 1958 she made frequent visits to West Penwith and became an associate member of the Penwith Society.
Her work is included in numerous collections including the Tate, the Victoria and Albert Museum, the Arts Council of Great Britain and the Museum of Modern Art, New York. She exhibited at the Tate Gallery in 1963, 1967 and 1985, and had a retrospective exhibition in the Sackler Galleries of the Royal Academy in 1994, the same year as her work Green and White was purchased under the Chantrey Bequest for the nation