Portrait of a Girl dates from 1884. 1
According to The Whitehall Review, Whistler was at work on a 'life size portrait of a pretty girl in a delightful dress of white and scarlet' in his studio in June 1884. 2
Notes:
1: YMSM 1980 [more] (cat. no. 311).
2: 29 June 1884; press cutting in GUL Whistler PC 6, p. 12.