Born in London, she suffered scarlet fever as a child, spending weekends and holidays at her grandparents' fruit farm in Kent. There she spent time painting, before enrolling at Saint Martin's School of Art between 1941-1946, and then the Royal Academy Schools, 1946-1947. She later enrolled at the Accademia di Belle Arti in Rome, where she met Alberto Burri, her partner of a few years. Blow and Burri travelled in Italy together before moving to and working in Paris, and Burri became a life long influence in her work.