Jane Loftus, Marchioness of Ely by W. & D. Downey
Her Wikipedia article, with this image, is here. The image was very grainy and heavily spotted so the more prominent spots throughout the image were removed with Photoshop and the background above the floor line was blurred with Photoshop by gogm.
Lady Jane cannot sit all the way back in her chair because the bustle is there. The tassels appear to mark the edge of her cuirasse bodice, made of striped cloth, while a tablier of the same material descends further down. Her bodice has a deep square neckline edged with a lace ruff.
Keywords: W. & D. Downey, Jane Loftus, Hope-Vere family, Loftus family, Marquise, British, curly coiffure, square neckline, ruff, lace, three quarter length sleeves, fringe, engageantes, bustle, cuirasse bodice, tablier, under-skirt, ruffles, earrings, bracelets