Initially, she associated with Frances Benjamin Johnston, who later became her lover, living and working with her from 1909 for 8 years. Together they also established a firm called "Johnston-Hewitt Studio" in New York City in 1913 which functioned till 1917. They became well known in the field of architectural and landscape photography and took many pictures of famous buildings and gardens which were titled "Miss Johnston and Mrs. Hewitt" or "Frances Benjamin Johnston and Mattie Edwards Hewitt."[2][3][4]