Born in Warren County, Georgia, Dillon grew up in Augusta, where she developed an interest in gardening. She studied at Peabody College (now part of Vanderbilt University) in Nashville, graduating in 1890. Returning to Augusta to teach, her twenties were beset by tragedy marked by the death of her husband, and the onset of hearing loss, a condition which would worsen throughout her life and eventually, paired with blindness, put an end to her career.
In 1907, she began studies in landscape design, taking courses at Columbia University and Harvard. Entering into private practice in Augusta, Dillon’s projects included residential landscapes and work in the public sector, including parks and school landscapes. From 1914 to 1917, she completed commissions for post offices and custom houses for the U.S. Department of the Treasury. After World War I, she participated in the design of war memorials; her most significant commission was the 1920 design of Memorial Park in Sumter, South Carolina, for the Sumter City Council. This project led to her full-time appointment as city landscape architect, a position she held until 1948.
Over the course of her career, Dillon wrote and published a number of articles and pamphlets. In the 1910s and 1920s, she wrote about southern gardens for The Florists’ Exchange, House and Garden, and The Flower Grower. Her 1922 book, The Blossom Circle of the Year in Southern Gardens, which gave advice to amateur southern gardeners (much of it directed at women), established her reputation as an expert on the topic.