From eBay; Boris Wilnitsky watermark removed with Photoshop.
Elizaveta's hat is adorned with flowers or, probably, feathers in this portrait. It is not a bonnet because the back of the head is uncovered.
Keywords: Elizaveta Markovna Olenina, Poltoratsky family, Olenin family, Princess, Russian, curly coiffure, feathered hat, strap, bows, vee neckline, bertha, close sleeves