Rosamund Haden, sister of the surgeon and etcher Francis Seymour Haden, married John C. Horsley, RA.
Rosamund Horsley is recorded in the 1881 census as aged sixty, and then living at 1 High Row, London. Haden's wife, Whistler's half-sister Deborah. kept in close contact with 'Rose'.
UK census 1881, from http://www.familysearch.org (accessed 2004).