Letty began her first work in the art field in 1925 when she began work at the Onderstepoort Veterinary laboratory. Here she had to record in detail the post mortem appearance of various animal diseases and abnormalities. This was before the time of colour photographs. In 1927 she was moved to the Division of Plant Industry in the Department of Agriculture where she painted flowers.
During her period of work she completed over 740 plates for Flowering plants of Africa together with some other work. She was regarded as a leading botanical artist, and three of her works were accepted for the new national monetary coin series in 1961.
In 1973, Letty published on the species Bothalia, illustrated by herself. She also published various other smaller works. Her contribution is remembered in the names Aloe lettyae Reynolds and Crassla lettyae Philips.