Born in New York City and raised in a patrician world, Coffin pursued a career in landscape architecture out of financial necessity, preparing at the Massachusetts Institute of Technology as a special student, and traveling to Europe to study great gardens. Through her friend Henry Francis DuPont, she received many client referrals as well as her most important commission, Winterthur, near Wilmington, Delaware. Other important commissions included Gibraltar, also in Delaware, and Clayton, the estate of Mr. and Mrs. Childs Frick in Roslyn, New York. Clayton has since become the home of the Nassau County Museum of Art. At the height of her career, she designed over 50 significant estate gardens in the northeastern U.S. In her book, Trees and Shrubs for Landscape Effects, she articulated her design theory. Though less well-known than her contemporary Beatrix Farrand, Coffin was recognized for her refined and elegant designs, both formal and naturalistic.