She was the elder daughter of Tristan de Clermont, Count of Copertino, and Caterina Delegate Balzo Orsini. She was also the niece and heir of childless Giovanni Antonio del Balzo Orsini, Prince of Taranto. On 30 May 1444/1445, Isabella married Ferdinand of Aragon, then Duke of Calabria (1423–1494), natural son of Alfonso V of Aragon who had recently conquered the Neapolitan kingdom from French Angevins, and thus was the new liege lord of Isabella and her family.
Her maternal grandmother Maria was queen consort of Naples from 1406 until 1414. Alfonso arranged this marriage in order to give a good future to his favorite bastard son, by giving him his own principality by marriage. The marriage also strengthened the king"s grip on the current lords of Taranto.
By that point, they had several children of their own, the eldest being the 10-year-old Alphonso.
Isabella also inherited the Brienne claim to the Kingdom of Jerusalem. Isabella died on 30 March 1465, and was buried in San Pietro Martire.
She had six children with Ferdinand:
Alfonso II of Naples (4 November 1448 – 18 December 1495). Eleanor of Naples (22 June 1450 – 11 October 1493).
The latter daughter was consort of Ludovico Sforza.
Frederick IV of Naples (19 April 1452 – 9 November 1504). John of Naples (25 June 1456 – 17 October 1485). Later Archbishop of Taranto (and/or "Strigonia", apparently Esztergom in Hungary) and then Cardinal.
Beatrice of Naples (14 September/16 November 1457 – 23 September 1508).
She was Queen consort of Matthias Corvinus of Hungary and Ladislaus II of Bohemia and Hungary. Francis of Naples, Duke of Sant Angelo (16 December 1461 – 26 October 1486).
