Howard was born in Long Branch, Ontario, in 1926, the younger of two children. Her father, Thomas Howard, a secondary school teacher, was an English immigrant. Her mother, Helen Mackintosh, who was born in Winnipeg, was of Scottish ancestry. Having decided early to become an artist, Howard studied at the Ontario College of Art in Toronto from 1948 to 1951, where she was a pupil of Will Ogilvie, who taught her figure drawing, and Jock Macdonald, who taught her painting and composition. In her final year she won the silver medal in drawing and painting.
Howard taught art classes in Toronto until 1953, when she moved to London, England, where she studied at Saint Martin's School of Art, immersing herself in the English landscape and the cultural life of postwar London. She also travelled to Europe to visit the art museums of Rome, Venice, Florence, Paris and Madrid, and saw the Paleolithic cave paintings at Lascaux in southwestern France, an experience which influenced many of her later illustrations. In London she met her future husband, the Canadian poet, Richard Outram. Returning to Canada in 1956, Howard and Outram made their home in Toronto for the next 46 years.
In the late 1950s and early sixties Howard showed regularly at the Picture Loan Society, a Toronto gallery established by Douglas Duncan in 1936 to present the work of contemporary Canadian artists such as Emily Carr, Fred Varley, David Milne, Lawren Harris and A.Y. Jackson. Several Canadian public collections possess Howard drawings and paintings acquired through the Douglas Duncan estate, as Duncan was also a collector of her work.
In 2002, Howard and Outram moved to Port Hope, Ontario, but soon after their arrival Howard fell and broke her hip. While undergoing surgery on 7 December in Peterborough, Ontario, she suffered a pulmonary embolism and died on the operating table.