Daughter of Lt-Col John Erskine (1660-1737), Deputy Governor of Stirling Castle, and Euphemia Cochrane (1693-1720/1). Married (1738) to Alexander Boswell. Mother of James, John and (Thomas) David Boswell.
Her mother died when she was 2 years old, and her father was almost 60 when she was born. As a result, she was brought up by her grandmother (Mary Bruce (d. 1739), daughter of the 2nd Earl of Kincardine) and her aunt Anne Cochrane (d. 1779), Lady Preston, who was married to 4th Bart of Valleyfield.
According to descriptions by James and Alexander Boswell, she was a pious, dutiful and loving women. She also suffered from some degree of hypochondria, as JB wrote in his sketch to Rosseau in 1765.