Born in Amoy, China, in 1933, Mignonette received her initial training at the Russian Art Academy in Shanghai and Chao Shao-An Studio in Hong Kong. In 1958, Mignonette received a full scholarship to attend Ohio University in Athens, Ohio, and graduated with a Bachelor of Fine Arts degree, cum laude. One year later, she completed her thesis and a solo exhibition, Chinese Painting and Western Emblems: A Comparative Study, and received a Master of Fine Art degree. She was a professor emerita of painting at the University of Michigan School of Art & Design, having taught there for more than 30 years.
Her work is represented in numerous private and public collections, such as Springfield Art Museum, Springfield, Missouri; Ford Motor Company, Dearborn, Michigan; and Proctor & Gamble, Cincinnati, Ohio.