Madame Subercaseaux (born 1860) twenty years old at the time, was the newlywed wife (married 1879) of the Chilean consul to Paris. The following is from her diary. 

It was in Paris during the Spring of 1880 that Sargent painted my portrait which won the prize the following year [2nd place at the Salon]. Shortly before this, when we were visiting the annual exposition, Ramon noted a small picture of an oriental woman perfuming her clothing with aromatic incense from a brazier [Fumee d'Ambre Gris]. This picture was in clear colours - white and grey. In the catalogue, he located the name of the artist, John S. Sargent, and noted he was from the United States. A few days later, arrangements were made for Sargent to paint my portrait. We went to his atelier and found it to be very poor and bohemian while the artist himself seemed a very attractive gentleman and therefore we treated him as a real friend. He was very young at the time, only 24 years of age, but he was a man of very pleasant manners. He came to our apartment to arrang the setting, clothing and other details. He studied every single detail very carefully and was entirely free to arrange the composition of the portrait as he wished. It was not difficult to pose for him as his hours of work were neither long nor heavy. His way of painting was light, as his work showed afterwards. He concentrated on each detail and took great care of the effect of each object and colour. He was a man of great skill who felt secure and at ease while working. He was very fond of music and had me play for him. He brought me several pieces from Gottschalk, music composer, whom he admired very much, specially his interpretations of Spanish and South American dances. He had been in Spain a short time and everything about that country left its impressions on him and from it he drew his inspirations. His teacher was Carolus Duran, and from him he became a great admirer of the great Spaniard Velazquez. 
(The Complete Paintings Vol. 1  quoting from Subercaseaux family papers )

• See the year in review 1880
• A moderated discussion:  Subject: Has the Painting been restored and/or repainted?