After Ramsay's return from Italy in 1738 his confidence soared. It is recorded that he told Alexander Cunyngham that he has 'put all your Vanlois and Soldis, and Ruscos, to flight and now play the first fiddle my Self.'

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.

Van Aken was called on to paint the draperies. Such was the competition 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.