Sia lived and studied in
Beijing in the 1920s, with her husband, a medical school professor. They moved to Hawai'i in 1939. She was director of the Oahu
YWCA in the 1940s, and served on the branch's board. She taught classes in Chinese cooking at the
YWCA in Honolulu from the 1940s into the 1970s. She led her classes on trips through factories, restaurants, and markets, to understand the larger context of her recipes and techniques. and
Mary Sia’s Chinese Cookbook (1956), which went through multiple editions. "I have spent a lifetime in opening new culinary worlds to thousands of people, both in the East and the West," she explained in the preface to her cookbook. ==Personal life==