From Wikimedia; bluish tint removed.
Olga's dress has wide lace-trimmed epaulettes emerging in ca. 1830 style and, possibly, imbecile sleeves.
Keywords: Olga Naryshkina, Olga Potokich Naryszkin, Olga Potocka, Potoka family, Naryszkin family, Countess, Russian, straight coiffure, bun, neck band, pleated bodice, off shoulder vee neckline, modesty piece, imbecile sleeves, cuffs, full skirt