She wears a linen shift which imitates classical drapery and a large white feather adorns her headdress.
The Duke (later King James II and VII) and Duchess of York (previously Anne Hyde) were painted by Peter Lely in between 1668 and 1670. Their two daughters, Mary (left) and Anne (right), later Queen Mary II and More
Public domain image, 18th-century female portrait, aristocracy, free to use, no copyright restrictions - Picryl description