Yvonne Isabella Forster was the daughter of the barrister Mathew Forster and Amy Leslie Forster, née Worth. She later married Henry Dyson. They had two daughters, Maude Elizabeth and Nina Dorothy.
She was drawn by JW as a child, in Portrait of Miss Yvonne Forster (M.838).
MacDonald, Margaret F., James McNeill Whistler. Drawings, Pastels and Watercolours. A Catalogue Raisonné, New Haven and London, 1995.