Self-Portrait with Two Pupils, Marie Gabrielle Capet and Marie Marguerite Carreaux de Rosemond, Adélaïde Labille-Guiard; oil on canvas, roughly 83 x 59 inches (210 x 151 cm). Link is to the Metropolitan Museum of Art, which has the original in its collection and offers zoomable and downloadable images.
Adélaïde Labille-Guiard was one of only four female students allowed into France’s Académie Royale when she was there in the 1780s. (Another was Elisabeth Vigée Le Brun.)
While it’s of course unlikely that she painted while dressed this way, it was common at the time for artists whose self-portraits showed them working to appear in their finest.
[I’ve taken the liberty of brightening the Met’s image. While I haven’t seen the original of this painting, it’s been my experience — based on images of work that I have seen in person — that museums often display images of works in their collections that are much darker than the original paintings. This appears deliberate, though I don’t know the reasoning behind it.]