An elder brother, Antrobus, was killed in the
Flanders trenches in 1916. Another brother, John Brocas Harris ( –1967) had earlier emigrated to South Australia, served at
Gallipoli with the Army Medical Corps and was badly wounded. He married Gwendoline Mary Colyer ( –1959) in 1917, and settled in
Gawler, where he was a noted horticulturist and horticultural inspector at Gawler, and later at the Government orchard, Blackwood. His eldest son Dr. Ian Harris born 12 February 1920 was awarded DSC for navy heroism. In response to his urging, Mary and her parents emigrated in 1921. In 1922 she accepted a position with the
SA School of Arts and Crafts, where she was to teach for 30 years in a wide range of mediums: oil and watercolor, lino and woodblock printing, tapestry and embroidery. Harris was a longtime member of the
Royal SA Society of Arts (1922–67) and also exhibited with the
Contemporary Art Society. Fellow teachers included her friend
Ruth Tuck. Students included
Rex Wood,
Jacqueline Hick and
John Olday. She lived at "Bundilla", 116 Walkerville Terrace, Walkerville, which she filled with her own and her students' art, and with a lovingly tended native bird garden punctuated with sculptures by
William Ricketts and her nephew Quintin Gilbert Harris (1928–1985), son of J. B. Harris (above). Her bequest of this home to the
Town of Walkerville was declined, but the Council did accept the many works of art, including sculptures by her friend
Ola Cohn. She was a leading member of Adelaide's
Lyceum Club. ==Personal life==