I have not been able to find out anything about Olga, much less her mother, other than they were portrayed frequently.
From Wikimedia.
Little Olga reaches towards her mother who wears what appears to be an Empire adaptation of traditional Russian festive dress that is lavishly embroidered with gold thread, even on her veil.
Keywords: 1817, Lefevre, Olga Orlova, Bariatinsky family, Davidov family, Russian, bandeau, crown, veil, high neckline, partlet, square neckline, long full sleeves, cuffs, Empire waistline, close skirt, tassels, necklace, earrings, shoes