I am interested in how painters work, so from time to time present example of sketches, studies, and uncompleted paintings that offer insights.
Below is a set of such images by Waterhouse.
I rate this as an oil sketch rather than a study for a more finished painting, but I might be wrong.
Focus is on her face, the rest is roughly indicated.
Her face is largely finished, so I wonder if Waterhouse was thinking of making a painting of Medea only. Given the roughed in background, it's possible that this was an unfinished work.
This has the look of an unfinished painting rather than a study. An Internet search turned up no other Waterhouse image of that title.