Who is Megan Fitzgerald from Cathedral and what is their importance?

Megan Fitzgerald was a twenty-one-year-old member of the IRA, as well as one of the Fenian terrorists at St. Patrick's Cathedral. Megan grew up with the violence in Belfast, and she is third in command of the operation at the cathedral. Megan is assigned to the choir loft area with Jack Leary, who kills her before the bombs are set to go off.