Nichols began her career as a painter, studying under prominent artists and training at the Art Students League in New York and in Paris and Rome. Her passion for garden design was influenced by her time at the Cornish Art Colony, where she studied under Charles Platt. Over her 40-year career, Nichols designed 71 gardens across the United States. Nichols published three books on European garden history and contributed to prominent magazines. Beyond her design work, Nichols was an active suffragist and pacifist, participating in the Boston Equal Suffrage Association for Good Government and the Women’s Peace Party, and hosting influential discussions at her home. After inheriting the house in 1930, she developed a collection of American decorative arts and worked on a manuscript about New England architecture. In 1961, her home opened to the public as the Nichols House Museum, preserving her legacy in art, design, and social reform.