Who was she? I don't know. She shared her name with a Lady-in-waiting to Katherine Howard, short-time wife of Henry VIII. Outside of this portrait, there seems to be nothing about her.
Lady Isabella strikes a British Ice Queen pose for this John Vanderbank portrait.
Keywords: Vanderbank, British, long straight coiffure, scoop décolletage, hair jewelry, chemise, modesty piece, quarter length close over-sleeves, cuffs