Eustochium is a daughter of St. Paula, a follower of St. Jerome. See the Golden Legend's life of St. Paula (html or pdf). In the image at left she and
her mother are in nuns' habits because they were abbesses of convents
that Jerome founded in Bethlehem.
Also see Claude Lorrain's Embarkation of St. Paula Romana
More of St. Jerome
More of St. Eustochium
National Gallery of Art