The Bourne catalog has this entry, "van Aken was called on to paint the draperies. Such was the competi- tion for his work between Ramsay and Thomas Hudson they each offered him eight hundred guineas a year for exclusive rights to his services. He was held in high esteem by many artists of the time –Hogarth even called him ‘the tailor’. The striking red silk dress highlights her flushed cheeks to give her a markedly youthful appearance which combined with the delicate precision with which Ramsay records her features lends the sitter a demure and intimate air.
The sitter is the younger daughter of John Morley Trevor (1681–1720) of Trefalyn and Glynde, Denbighshire and his wife Lucy Montague (1678–1720), sister of George Montague, 4th Earl of Halifax. There is another portrait (three-quarter length) of Ruth Trevor by Ramsay dated 1748." According to A Genealogical History of the Dormant, Abeyant, Forfeited,and Extinct Peerages of the British Empire, p. 538, she died in 1764 with no marriage or children recorded.
From the Bourne catalog via pinterest.com-lucindabrant-18th-century-artladies-.