Frances Stuart's combination of waistless dress with regal robes makes an interesting contrast in this Lelyesque portrait by Jan van der Vaart. Her Wikipedia article is here.
From Wikimedia; detail-enhanced by gogm.
The National Portrait Gallery, London has a writeup about Jan van der Vaart here.
Keywords: van der Vaart, Duchess, British, Frances Theresa Stewart, Britannia, long curly coiffure, scoop neckline, split bodice, chemise, elbow length puffed sleeves, no waistline, full skirt, robes, coronet, clasp, jeweled robes