From Wikimedia.
Here is another Lely portrait of a woman, this time with a lamb, in pseudo-pastoral style. He rddress has slashed sleeves notched at the bottom held together by clasps.
Keywords: 1665, Lely, British, straight coiffure, off shoulder scoop neckline, chemise, modesty piece, puffed under-sleeves, puffed notched sleeves, slashed sleeves, full skirt, clasps