Mary Ann Edington was born in Glasgow, Scotland, on 18 June 1897, the daughter of Edward Edington, a packing box maker, and his wife, Mary Ann Rogers. She gained a BA degree and her mathematical skills gained her a position with William Arrol and Company, engineers. During the First World War she became a crane operator and supervisor for the firm in France and England.
Mary Edington sailed to New Zealand in 1920. She married Horace Ellen, a wool valuer, at Knox Church, Dunedin, on 28 May 1921: they were to have two children. The couple went to live in Fendalton, Christchurch. Horace's business trips left Mary alone for lengthy periods, and at various times between 1924 and 1931 she took courses at Canterbury College School of Art, winning first prize for craft in 1927. By 1928 the Ellens had moved to the city centre, where Mary was the representative for Livingstone Brothers, paper merchants of Glasgow. Two years later they settled at Woodend, North Canterbury. Here Mary became involved with the Plunket Society and was secretary of Woodend School Committee from 1938 to 1940.
Improving the lot of rural women became a major concern for Mary. She was a founder and the first president of the Woodend–Waikuku branch of the Women's Division of the New Zealand Farmers' Union, holding office from 1932 to 1936. In her local district she established the union's emergency housekeeper scheme to relieve mothers at childbirth, and when they were ill and overworked. From 1933 to 1935 she was also on the division's North Canterbury committee.
In 1935 Mary Ellen headed the poll in her constituency for the North Canterbury Electric Power Board, becoming the first woman in New Zealand to win a seat on an electric power board. She was deputy chairman in 1944–45. To increase her knowledge of electricity, for 3½ years she attended lectures for the Institution of Electrical Engineers examinations.
As a board member Ellen was recognised as 'a staunch champion of her sex'. Appreciating that electricity would significantly reduce the time and energy women spent on housework, she was particularly concerned to reduce the price to the domestic consumer. In this she was soon successful. She made little headway, however, in her other goal of making credit for the purchase of ranges and water-heating equipment available to housewives. Outnumbered and frustrated by her male colleagues, she allegedly delighted in confusing them by using Scottish dialect.
Mary Ellen was prominent in patriotic work in the Rangiora district during the war. She chaired the Women's War Service Auxiliary, and was especially successful in collecting war loans. In 1943 the government appointed her to the rehabilitation committee. In recognition of this work, her practical help in the community and her service on the Power Board, she was appointed an MBE in 1946. In 1947 she was elected to the North Canterbury Hospital Board, sitting on the benevolent committee, and, from early 1949, the building committee.
Tall and slim, Mary was noted for her forthright speech and 'crusading zeal'. While she endorsed domestic feminist issues in public life, her personal interests included what her contemporaries regarded as male preoccupations. A woman of means, Mary Ellen was unusual in her day for going to work outside the home. In 1938 she opened her own hairdressing salon in Rangiora, staying in business until after the Second World War. Her behaviour was unconventional: to catch the warmth, she hitched her skirts over the electric fires at Power Board meetings; she strapped herself to the chimney of her house in order to paint its upper storey; and she once gained notoriety for being charged with drunken driving. She is also remembered for holding fund-raising functions in her home and its garden.
By 1949 the Ellens had moved to Waikuku Beach. Horace died in June that year and Mary died two months later, on 19 August 1949, while still a member of the power and hospital boards. She was survived by her two sons.