Canadian by birth, Mary Bell studied in Montreal with Robert Harris, and subsequently in New York at the Art Students League with William Merritt Chase, and at the Academie Colarossi in Montparnesse, Paris (1891).

She had arrived in St Ives in 1893 from Ontario, having been for a brief period a member of the staff of the Victoria School of Art in Montreal (1892). In St Ives she met her future husband, Charles Herbert EASTLAKE. As Miss M A Bell, she painted from Tregenna Terrace in 1896 and maintained a studio in Regent's Park. The couple designed and made enamels for jewellery, and travelled extensively on the Continent.

In 1911 the couple were painting from a studio in Chelsea, London. During this period they lived in Warwick Square, London and later at 'Hollywood' in Croydon.  By 1939 they had returned to Montreal, and shortly thereafter to Ontario. She died in Ottawa in 1951.

She exhibited regularly at the RA. Her studies of Dutch child-life had a great success in England and America.