Marvin was born in Attington, near
Tetsworth, in 1872. Her parents, Mary Seymour and Alfred Deverell JP, were
Congregationalists. Her father was a farmer and he also sold coal. She was educated at home until she attended a private school in Weston-super-Mare. In 1892, she gained access to
Somerville College, Oxford where she graduated in Modern History, but did not receive a degree because she was a woman. While she was there in 1894 she was one of the seven founding members of the "Associated Prigs". This was the unofficial name of the discussion group that met on Sundays evenings. The first meeting was in her room. They never agreed a name or leader but the group would keep notes and the links established were valuable after they left Somerville. Other founder members were
Mildred Pope and
Eleanor Rathbone and other early members were
Margery Fry and
Hilda Oakeley. She ceased to be inspector in 1904, but she carried through her ideas within the
National Union of Women Workers. She argued that teachers needed to trained in physiology. She argued that the health of children could also her improved by appointing more female school inspectors and female school managers. Marvin belonged to the committee which presented the Women Graduate Suffrage Petition to the Liberal Prime Minister
Henry Campbell-Bannerman in May 1906. Marvin died in
Berkhamsted in 1958. ==Private life==