They cannot be located in thepeerage. There is a Martha Blount from the previous century listed there.
From myartprints.co. They list it as being with a private collection. The Fitzwilliam Museum of the University of Cambridge may have it or another rendition.
Here are two examples of British casual dress. The bodices appear to collapse on to the waistlines.
Keywords: 1716, Jervas, Blount family, British, long straight coiffure, floral headdress, scoop décolletage, chemise, modesty piece, cuffs, criss-cross bodice, elbow length close sleeves, three quarter length close sleeves, cuffs, natural waistline, waist band, shallow vee waistline, full skirt, wrap