I cannot find anything about her.
From the lost gallery's photostream on flickr.
This portrait shows 1780s style persisting away from France. The dog obscures the lace edge of her fichu.
Keywords: 1790, Lawrence, Countess Susanna Archer, straight coiffure, ribboned cap, high enclosing neckline, neckline ruff, fichu, lace, waist band, long tight sleeves, ruffles, full skirt, apron, pendaloque earrings