An 1830 portrait, this image, naming the sitter as Elisabeth Alexeevna Tolstoy was posted first, while I found this listed only as Countess Tolstoy, but the faces match.
I can find nothing about her. According to this Wikipedia article, her husband fought in the Napoléonic wars, losing a hand and suffering other wounds. After the wars he left Russia to spend his time in Italy and Switzerland. The article continues, "Count Osterman-Tolstoy was married to Princess Elisabeth Alexeevna Galitzine (1779–1853) from 1799; they had no children. He had foreign mistresses and a lot of illegitimate children. There is an engraving, published in Pisa in 1827, on which Count Osterman-Tolstoy is depicted sitting beside a pram with a sleeping baby and two older children playing nearby; the inscription says, ‘Je me flatte que c’est les derniers faries (sic). A 55 ans il est temps de faire la clôture.’ (I flatter myself with the thought that it’s my last extravagancy. At the age of 55 one must stop).”
From liveinternet.ru/users/2010239/post179445331.
The Countess sports a coiffure that resembles the key of a wind-up toy while wearing a dress with a sawtooth bertha. Fashion plates of the era, like this one, emphasized the broad shoulders.
Keywords: 1829, Bryullov, Countess Elisabeth Alexievna Ostermann-Tolstoy, Galitzine family, Ostermann-Tolstoy family, Countess, Russian, curly coiffure, knotted bun, earrings, partlet, high neckline, collar, bow tie, criss-cross bodice, off shoulder vee neckline, sawtooth bertha, upper puffed sleeves, belt, jeweled buckle