She went on to marry Ruairí Ó Domhnaill, Earl of Tyrconnell at some point after 1603 when she was around fourteen. Her son, his heir was born on October 1606 in Maynooth, and became known as Hugh Albert or Hugh O'Donnell, 2nd Earl of Tyrconnell, having inherited the title upon his father's death in 1608, and long before the attainder of 1614. Brighid was pregnant when her husband fled the country in the Flight of the Earls (Sept 1607) with his son. There is evidence that her husband tried to have her join him in Europe but that the English authorities prevented it. Brighid went to England where their daughter Mary Ní Dhomhnaill was born. Rory died in Rome on 12 August 1608. Mary was placed under the patronage of the King and Brighid was sent back to Ireland. She later married Nicholas Barnewall, 1st Viscount Barnewall from Turvey, County Dublin. They had nine children.