Maria Pavlovna, Grand Duchess of Saxe-Weimar-Eisenach by ? (Weimar Castle - Weimar, Thüringen Germany)
This could be a work by Joseph Karl Stieler who died in 1858 and stopped working for the Bavarian court in 1855. This portrait resembles one Stieler painted for the Saxe-Altenberg family in 1847-1848.
From Wikimedia; a linear flaw was removed from the curtain and spots were removed from her face and where the seam line on her shoulder ends with Photoshop by gogm.
Maria Pavlovna appears to be wearing a flounced dome crinoline dress, a gorgeous lace wrap, and a floral headdress on a typical straight "Victorian" coiffure. The wrap conceals her bodice. There appears to be a seam or a line of beads running along her shoulder, making her neckline a mystery.
Keywords: Maria Pavlovna (1786-1859), Grand Princess, Grand Duchess, Romanov family, Wettin family, German, straight coiffure, floral headdress, wrap, lace, quarter length tight sleeves, crinoline, bows, flounces