Daughter of Sir William Carr of Etal (d. 1777). In 1762 she married James Hay (d. 1778), 15th Earl of Erroll, with whom she had twelve children.
Boswell met Lady Erroll (as she then was) when he visited Slains Castle together with Dr Johnson on August 24, 1773. Boswell wrote, that "Lady Erroll received us politely, and was very attentive to us in the time of dinner" and that "After dinner my lady made her young family stand up in a row. There were eight, just steps of stairs, six girls and two boys, besides a young lady of four weeks old who did not appear. It was the prettiest sight I ever saw."