Her mother-in-law was Aurora Demidova. Biographic information about her can be found here.
From artsdiary365.wordpress.com/tag/nineteenth-century-art/.jpg; image made darker to bring out details and sepia tone removed by gogm.
Princess Maria wears a conical crinoline with a probable over-skirt with stepped edges.
Keywords: 1867, Maria Elimovna Meshcherskaia, Meshchersky family, Demidov family, Princess, Russian, jeweled headdress, off shoulder vee neckline, modesty piece, pleated bodice, ruffles, quarter length tight sleeves, crinoline, necklace, bracelets