I cannot locate anything about the sisters other than a one page scan from a 1971 issue of The Burlington Magazine. The image is included as an example of 1804 day dress. Ingres' portraits are excellent sources of information about fashion.
This is a superb illustration of 1804 day dress with scoop neckline, high waist, puffed up top, and close skirts. With no room for pockets, purses are now a necessity.
Keywords: 1804, Ingres, curly coiffure, scoop neckline, puffed cap sleeves, jacket, long upper puffed sleeves, Empire waistline, gloves, purse, wrap