[1] After William II's death in 1278, as he had no sons, per the Treaty of Viterbo, the princely title passed to the King of Sicily, Charles of Anjou, the father-in-law of Margaret's elder sister Isabella.
As J. Longnon commented, her rights on Achaea were "more than doubtful", and her claims were again disregarded by the principality's suzerain, Philip of Taranto, in favour of her niece Matilda of Hainaut and her husband, Louis of Burgundy.
Ferdinand was quickly enamoured of Isabella—described by the Catalan chronicler Ramon Muntaner as "the most beautiful creature one could possibly behold" and "the wisest lady in the world"—and the wedding was celebrated at Messina on 14 February 1314 in great pomp.
[3] Margaret passed her titles and claims to them, and returned to Achaea in the summer of 1314, where she was imprisoned by the Angevin bailli Nicholas le Maure at the castle of Chlemoutsi, where she died in February or March 1315.
[4] Ferdinand invaded Achaea and tried to claim the Principality from Louis of Burgundy, but despite initial success fell in the Battle of Manolada in July 1316, and the remnants of the Majorcan army withdrew soon after.