She was curator of Prints and Drawings at the India Office Library and wrote extensively on the collection and studies on them.
Born Mildred Agnes Bell, she attended school in London.
Bill had passed the Indian Civil Service examination and was in the School of Oriental Studies, London.
After marriage Bill worked in Bihar for nearly a decade and on his return to England he became Keeper of Indian Art at the Victoria and Albert Museum and was a leading scholar of Indian court painting and the Company style.
Her later publications included a study of the Daniell aquatints of India (1980), the V&A exhibition catalogue India Observed (1982), and studies of William Simpson's Indian sketchbooks (1986) and the prints and Company paintings associated with James and William Fraser (1989).