Born in 1881, Preston was the youngest of 5 children. Both of her parents were avid gardeners, which inspired her love of gardening. As a child, she helped them with their gardening and maintained her own flower bed. Preston lived in an exciting time for horticulturalists – there were many exciting and exotic new plants coming in from Asia and South America. To begin her formal education in horticulture, she took a year to study at Swanley Agricultural College.

After the passing of her mother and father, she followed her sister Margaret to Canada. At the time, women were encouraged to only pursue gardening as a hobby for exercise and aesthetics. Undeterred, Preston decided to pursue her career by enrolling at the Ontario Agriculture College (OAC). After a year, she gave up her studies to assist Professor J.W. Crow at the OAC, where she worked to breed fruit that ripened more quickly and was more resistance to disease and insects. In 1916, she successfully cross-bred two varieties of lilies, making her the first female hybridist in Canada. The fruit of her efforts, the George C. Creelman lily, is often used as a parent for modern hybrids.

In 1920, she was hired to work at the Central Experimental Farm (CEF). Over the course of the next 26 years, she developed over 200 individual hybrids, crossing existing plants to produce disease-resistant varieties with abundant flowers. The various lily, lilac, rose, columbine, Siberian iris and crabapples she developed for the Canadian climate were released through the CEF and its satellite stations across Canada. She was the first CEF employee to specialize in ornamental plant breeding. She defied gender expectations throughout her career, eventually becoming a Dominion Horticulturalist.