This portrait was acquired by William Byrd II. The subject was likely the wife of Sir Robert Southwell, née Elizabeth Dering (1649-1682), or more likely, the daughter of Sir Robert Southwell, also named Elizabeth. William Byrd II would not have known Elizabeth Dering Southwell. However, he socialized with Elizabeth Southwell the younger as recorded in his London Diary, 1717-1721. The portrait remained with Byrd descendants through at least the mid-nineteenth century.
Reference: “Lady Betty Southwell” was bequeathed to Richard Willing Byrd in Mary Willing Byrd’s Will.
See: Mary Willing Byrd, “The Will of Mrs. Mary Willing Byrd, of Westover, 1813, with a List of the Westover Portraits,” Virginia Magazine of History and Biography 6, no. 4 (April 1899): 345-358; David Meschutt, “William Byrd and His Portrait Collection,” MESDA Journal 14, no. 1 (May 1988): 18-47