From Wikimedia; removed spots with Photoshop and filled in shadows.
Mary Isabella's coiffure and tall turban headdress and feathers must stand about a half meter above her head.
Keywords: Smirke, Reynolds, Mary Isabella Somerset, Duchess of Rutland, Somerset family, Manners family, Duchess, British, high straight coiffure, feathered turban, vee neckline, three quarter length notched close under-sleeves, elbow length notched full over-sleeves, waist band, low waistline, close skirt, drapery, robes