A native of Cincinnati, Pendleton displayed an interest in gardening and landscape design as a young woman. She was a founder of the Cincinnati Garden Club and became its president in 1915. Pendleton soon relocated to the Boston area to attend the Lowthorpe School of Landscape Architecture in Groton, Massachusetts, graduating in 1917. Shortly thereafter, she returned to Cincinnati. Around 1922 Pendleton moved to New York City, where she set up her first office. Much of her work was concentrated around Cincinnati, Long Island, and Princeton, her preferred practice being to return to each client for yearly consultations. After her marriage in the mid-1930s, she and her husband resided in New York City, also keeping a cottage in Chilmark on Martha’s Vineyard, where she designed gardens for her neighbors. In 1938 Pendleton was commissioned by the Trenton, New Jersey Garden Club to rehabilitate a colonial-era garden for Trent House, the early eighteenth-century home of William Trent, the city’s founder. Her plan included an herb garden, a small pear orchard, a boxwood circle with a groundcover of English ivy, 300 yews planted in close proximity to each other, and brick paths. Creating this oasis in a factory district inspired her to encourage the planning of such gardens in other such districts.
Pendleton wrote numerous articles, her first being “Striking Perennial Combinations” which was published in The Garden Magazine in 1920, and she lectured frequently. She was a member of the American Society of Landscape Architects (ASLA). Her projects were frequently published in garden periodicals and ASLA Yearbooks. Pendleton died in Princeton at the age of 74.