In another thread, a few years back, I gave the explanation as to why the lady "cam trippin doon the stairs" when she heard Johnie Faa singing---no magic involved, she recognised the song and the singer from her previous involvement with Sir John Fall of Dunbar.
As a niece of the then King and daughter of an Earl, a scandal of a child born out of wedlock could not be entertained so she was married out of hand to Kennedy of Cassillis who was created an Earl the year after the marriage, no doubt as part of an agreed marriage settlement, by the King her uncle.
The first child born to the lady, a son, did not live to reach adulthood and therefor did not become the second Earl of Cassillis.