Her article in thepeerage is here. Her last name is spelled S-T-E-W-A-R-T.
Lady Catherine is dressed in parliament robes for this portrait. The bodice is adorned with jeweled bands.
Keywords: 1747, Catherine Stewart, Lady Maxwell, Countess of Nithsdale, Stewart family, Maxwell family, wavy coiffure, hair jewelry, robes, quarter length over-sleeves, fur, jeweled arm bands, bodice, elbow length close under-sleeves, lace cuffs, full skirt, earrings, jeweled bodice ornament