In the early 1870s [Sidney] Colvin met the woman who was to become his wife, many decades later. Frances Jane (1839–1924), née Fetherstonhaugh, was married to Rev. Albert Hurt Sitwell (1834–1894), a Church of England vicar (variously in Calcutta, Stepney, and Thanet). The Sitwells had two sons: one died as a child, and one lived to early adulthood, Frances Albert 'Bertie' Sitwell (1862–1881). Their marriage was unhappy, so they lived apart and she earned her living as an essayist. https://en.wikipedia.org/wiki/Sidney_Colvin
Much debate has been made over the identification of the model for the Virgin in the final version of The Annunciation. It has been claimed that the likeness is to Georgiana but Mrs Sitwell as in this drawing, has so similar features as to be indistinguishable. Another tradition within their family holds that Julia Jackson ( mother of Virgina Woolf and Vanessa Bell) sat for the Virgin. All this could be true as the artist was looking for a generalized type suitable for the subject and could have taken features from any or all of them.