Born in Parson's Green, London, she was educated at Wimbledon until her family moved to Derbyshire in 1921, when she finished her education privately. From 1924 to 1931 she studied art at Manchester School of Art under Robert Baxter. After a period of illness she attended the Slade in 1934, but attracted by Walter Bayes' book on decorative art, she moved to Westminster School of Art where he taught. Under Bayes she realised her true interest lay in drawing and painting the human figure. She specialised in and is best known for her figure painting, although she did paint coastal and harbour scenes and teach.

She first moved to Cornwall in 1938, staying with the Sampson family at Keigwin Place in Mousehole until the outbreak of War in 1939, when she went to Stockport to teach. After the death of her parents, she returned to live with the Sampsons in 1945, there meeting Eric HILLER and Charles BREAKER. Together they formed the Newlyn Holiday Sketching Group in 1949, which became a regular Summer School for the next fifteen years.  Mort is a transitional figure working for the most part in Cornwall. A retrospective of her work, Fifty Years of Painting, was held at NAG in Summer 1985.