She was married in 1254 to Bohemond VI of Antioch. Antioch itself was eliminated when conquered by the Egyptian Mamluks in 1268. Bohemond VI then continued with the title of Prince of Antioch, though Antioch was no more. He also maintained the title of Count of Tripoli.
When Bohemond VI died, his heir Bohemond VII was only 14 years old, so Sibylla took over the regency for him. The regency was also claimed by Hugh I of Jerusalem, but Sibylla retained her position.
When Bohemund died, he was succeeded by his sister Lucia of Tripoli. Since the people of Tripoli were not pleased with having a foreign ruler, they offered Sibylla the county of Tripoli. This offer was withdrawn later and Lucia became princess and countess. Sibylla then withdrew to her brother Leo's court in Armenia.