18th century Charlotte Walsingham, Lady Fitzgerald by John Hoppner (auctioned by Sotheby's)
Baroness Charlotte's Wikipedia article, with this image, is here.
Here is a case of fashion unhinged from its French base casting about for something. In this case, it is van Dyck or Henrietta Maria revival with the jacket bodice featuring a big center tab and the sleeves with back-flared cuffs. The waist band is also set at the right height to evoke Henrietta Maria and the skirt is about the right shape. Her coiffure is carried forward from late pre-revolutionary bouffant styles. The ruff and back-flared cuffs can be called van Dyck revivals.
Keywords: Hoppner, Charlotte Walsingham, Boyle family, Fitzgerald family, Baroness, British, long curly coiffure, ribbon headdress, square décolletage, ruff, bows, partlet, jacket bodice, square neckline, long tight upper puffed sleeves, back-flared cuffs, lace, waist band, natural high waistline, close skirt