[1] Her father was Thomas Stewart, 2nd Earl of Angus.
She was married to Thomas, Earl of Mar with whom she had no children.
After her husband's death in 1374, she began an extramarital affair with William Douglas, 1st Earl of Douglas, who was married to the Earl of Mar's sister.
The countess secured a charter of her estates for her son, to whom, in 1389 the title was granted by King Robert II.
This biography of an earl in the Peerage of Scotland is a stub.