Snowden Treleaven was presumably the daughter of Francis Treleaven*, who collected land invertebrates for the South African Museum in the eighteen-nineties. In 1894 or 1895 she was appointed as assistant (the only one) in the Government Herbarium, under the Colonial Botanist, P. MacOwan*, in the Department of Agriculture. He found her an excellent worker and was impressed with her efficient control of the collection. In 1897 she presented the herbarium with a fine series of Euphorbia mauritanica ("Beesmelkbos") from Tulbach.
When MacOwan retired in 1905 and his post lapsed, the Government Herbarium was transferred to the South African Museum. There Miss Treleaven continued to take care of it, working under its honorary curator, H.H.W. Pearson*. Her work included answering numerous enquiries, especially from the Department of Agriculture, with the result that she left collecting to others. On 1 July 1907 she returned to the Department of Agriculture, leaving the herbarium in the hands of Dr E.P. Phillips. The next year she presented him with a number of plants of economic importance.
Back in the Department of Agriculture Miss Treleaven was at first a clerk under the agricultural assistant, Dr E.A. Nobbs*, but on 1 July 1908 was appointed as seed tester at the department's experimental station at Robertson. She retired from this post in 1912.