Frere was born in Gloucestershire, England on 11 August 1845. Her father, Henry Bartle Frere, served in the colonial administration of Bombay since 1834. In 1862 he was appointed Governor of Bombay.
Mary Frere published several poems and a play. Her most popular work was "Old Deccan Days; or, Hindoo Fairy Legends, Current in Southern India. Collected From Oral Tradition", printed in 1868. According to Frere's introduction, she began her collection of Indian folklore during long travels with her father. Her only female companion was a local ayah named Anna Liberata de Souza. She was a Christian descendant of the Lingaet caste from the Mahratta country. What started as an idle conversation evolved into a thorough recording and study of Indian culture. German orientologist Max Müller reviewed Frere's collection and wrote that her rendition of Sanskrit originals read like a direct translation of ancient Sanskrit. Frere's father assisted with the editing of the work and wrote an introduction to the first edition of Old Deccan Days.