All I can find out about her is here. She was an artist, poet, and Alexander Pushkin fell in love with her.
From Wikipedia.
This portrait shows Ekaterine Bakunina wearing an off-shoulder bateau neckline with modesty piece over a pleated bodice and under a knotted coiffure. She appears to be wearing amber jewelry.
Keywords: 1828, Sokolov, Ekaterina Pavlovna Poltoratskay, Ekaterina Pavlovna Bakunina, Poltoratskay family, Bakunin family, Russian, knotted coiffure, hair jewelry, off shoulder bateau neckline, modesty piece, pleated bodice, puffed sleeves, full skirt, wrap