Isabella Sydney’s brief article in thepeerage is here, but the keywords below assume this is Lady Anne Percy.
From artuk.org.
Lady Anne’s or Lady Isabella’s dress appears to have a vee waistline suitable for wearing in public.
Keywords: 1647, Lely, Anne Cecil, Anne Percy, Countess of Northumberland, Cecil family, Percy family, Countess, British, proto-hurluberlu coiffure, chignon, chemise, scoop neckline, fitted bodice, long puffed sleeves, cuffs, lining, vee waistline, close skirt, wrap