According to Paul Frecker's caption for this picture, she "was the only daughter of John Chambre, tenth Lord Meath, by his marriage with Lady Melosina Adelaide Meade, fourth daughter of John, first Lord Clanwilliam, was born in 1808, and married in 1832 Archibald, third Lord Gosford, by whom she had issue two sons and four daughters - Archibald, Lord Gosford; Hon. Edward Acheson, Coldstream Guards; Lady Gertrude, married to Mr. Francis Savile Foljambe; Lady Mary, married to Hon. Leopold W.H. Powys; Lady Katherine, married to Mr. Frederick W. Duncombe; and Lady Edith, unmarried." But thepeerage suggests she is Theodosia Barbazon, born ca. 1811. According to thepeerage, the daughter of John Chambre, Mary, died in 1806.
From Paul Frecker; image lightened, enlarged by half, and sepia tone removed by gogm (and re-added to the border only with Photoshop).