The motif of death and a maiden began during the black plague. It eerily reminds the viewer that death comes for all, even the young and pure.
Marianne Stokes, however was part of a movement called "Pre Raphael". This began in the late 1800's and saw a resurgence of popularity for Renaisance realism (Itself a resurgence of Classical Realism). At the time, in the late 19th century, art schools were pushing the ideals of Raphael as what artists should aspire to, however, the Pre-Raphaelites believed only the most serious subjects should be painted, and only in the most realistic way. It has been compared to the Emo movement of the late 90's and early aughts in music, literature and film.
Here, in Stokes' work, we see the angel of death visiting a young woman. The angel has the face of a woman, a large departure from renaissance and gothic depictions of Death and the Maiden, where death is a skeleton or other frightening thing. Death seems to be comforting the girl , rather than frightening, with her outstretched wing. There is sadness in both the faces showing even death has a conscious about the fragility of life.