All I can find out about her is that she was associated with the Marquise de Maintenon.
From the Sotheby’s Web site.
The Marquise wears in mid-century dress with an off-shoulder neckline framed by a taupe bertha, puffed sleeves, and a vee waistline. The jewels starting on her bodice continue straight down her skirt.
Keywords: van Egmont, Marquise de Montchevreuil, Marquise, French, straight coiffure, floral headdress, jeweled bodice, off shoulder vee neckline, bertha, elbow length puffed virago sleeves, jeweled arm bands, cuffs, girdle, deep vee waistline, jeweled close skirt, necklace, earrings, brooch, claspswrap