From Wikimedia.
This looks like 1840s dress with a bodice emphasized by darts, vee waistline, and simple skirt.
Keywords: Rothwell, Mary Wollstonecraft Godwin, Mary Wollstonecraft Shelley, Godwin family, Shelley family, British, straight coiffure, fitted bodice, off shoulder vee neckline, modesty piece, full quarter length sleeves, cuffs, bracelets, darts, vee waistline, full skirt, lace wrap