Mellis trained as an artist in Edinburgh and Paris. Between 1939 and 1946 she became part of the community of avant-garde artists living and working in and around St Ives. This included Ben Nicholson and Barbara Hepworth, who lived briefly with Mellis and her husband Adrian Stokes in 1939. Impressed by the work of Nicholson and Naum Gabo she became a constructivist. This work comprises pieces of driftwood, including mahogany, pine and plywood, which she collected from the beach at Southwold, where she moved in 1976. Some of the pieces of wood were already painted when found, others were painted by the artist. She refers to her walk on the beach as a hunt and the driftwood collected as her trophies.