Short answers, pulled from the story.
Lady Joan Fitzgerald died on the 2nd of January 1565 at Askeaton in County Limerick. Her death marked the violent end of the peace she had spent her life building between the Butlers and the FitzGeralds.
Lady Joan Fitzgerald was the only legitimate daughter and heiress of James FitzGerald, the 10th Earl of Desmond, and Amy O'Brien. Her father died on the 18th of June 1529 at Rathkeale, County Limerick, leaving Joan as heir general despite her granduncle succeeding as the 11th Earl of Desmond.
Lady Joan Fitzgerald was married three times to James Butler, Francis Bryan, and Gerald FitzGerald. Her first marriage to James Butler ended with his death on the 28th of October 1546, her second to Francis Bryan ended with his death on the 2nd of February 1550, and her third to Gerald FitzGerald lasted until her own death.
Lady Joan Fitzgerald served as a bridge between the Butlers and the FitzGeralds, using diplomacy and marriage to maintain peace in Tudor Ireland. She arbitrated between enemy camps, such as during the battle that never was in 1560, and her death on the 2nd of January 1565 caused the fragile truce to collapse within weeks.
After Lady Joan Fitzgerald died on the 2nd of January 1565, her widower the Earl of Desmond resumed the feud by attacking her son Thomas Butler. This conflict led to the Battle of Affane on the 8th of February 1565 and eventually resulted in the forfeiture and killing of her widower in 1583.