Lilian Louisa Britten passed the matriculation examination of the University of the Cape of Good Hope in 1904 and continued her studies at Rhodes University College, Grahamstown, where she was one of the early botany students of Professor Selmar Schonland*. She graduated as Bachelor of Arts (BA) with honours in botany in 1907, the degree being awarded by the University of the Cape of Good Hope. She then began to teach and in 1910 was at the Girls' High School in Oudtshoorn, from where she sent plant specimens to the Albany Museum, Grahamstown. After a few years she continued her studies at the Universities of Oxford, Cambridge and London. Upon her return to Grahamstown in 1918 she was appointed lecturer in botany at Rhodes University College. At some time between 1924 and 1930 she was promoted to senior lecturer, a post she held until her retirement in 1941.
Britten had an excellent knowledge of the flora of the Eastern Cape and was an avid collector, with over 7000 specimens to her credit. She collected mainly in the Grahamstown area. Her plants went to the herbarium of Albany Museum, the National Herbarium in Pretoria, and the Compton Herbarium in Cape Town. She was particularly interested in the genus Streptocarpus, but appears to have published only one paper on it, namely "Some Streptocarpus species from the Eastern Cape Province" (Journal of South African Botany, 1940, Vol. 6, pp. 21-30). At one time four species were named after her, Cineraria britteniae, Faucaria britteniae, and the succulents Delosperma britteniae and Haworthia britteniae.
Britten was one of the founders of the Old Rhodian Union, serving as its honorary secretary for the first 30 years. During those years she compiled a card index of all past students and was meticulous in keeping contact with them. In 1932 she was one of the founders of the Nature Reserve Society, formed to protect the flora of Mountain Drive, Grahamstown, and for many years served as its honorary secretary. She was a member of the South African Association for the Advancement of Science by 1910 and rejoined the association upon her return to South Africa from Britain in 1918. In 1931, when the association held its annual congress in Grahamstown, she served as joint secretary of Section C (which included botany).