Fay was born in Lahore, northern India (now Pakistan). Until the age of 15 she was schooled in India, when she was sent to boarding school in England. Her mother was artistic and her stepfather, a scientist and keen gardener, encouraged her to draw flowers. She started her illustrious career as a botanical artist as a research assistant to Professor Edwyn Isaac in the Department of Botany at the University of Cape Town.
Fay's paintings have been exhibited around the world and form part of important corporate collections including the Hunt Institute of Botanical Documentation, Pittsburg, USA; The Royal Botanical Gardens, Kew, London; Missouri Botanical Gardens, St Louis, USA; South African National Biodiversity Institute in Pretoria and Cape Town.