The portait to the left has the title "Elizabeth Delaval, Lady Audley (1757-1785), holding a book, with a water-spaniel, in a landscape." Her article in thepeerage is here. The middle left portrait is titled "Frances Delaval, the Hon. Mrs. Fenton Cawthorne (1759-1839), with a watercolour of a rose, in a landscape." A brief genealogy is found here. The center right image has the title "Sarah Delaval, Countess of Tyrconnel (1763-1800) with a white peahen, in a landscape." A genealogical sketch of Sarah, née Hussey, is found here. The portrait to the right is "Sophia Delaval, Mrs. Jadis (1755-1793), holding a Claude glass to the landscape." Her genealogical sketch is here. According to Wikipedia, a Claude glass is a darkened convex ("fisheye" effect) mirror.
Photos - John Hammond.
From nttreasurehunt.wordpress.com; spots removed from the images of Elizabeth, Frances, and Sarah Delaval with Photoshop by gogm.