The widow of a senior ISIS leader was charged with conspiracy in the death of American aid worker Kayla Mueller, the Justice Department said Monday. Mueller was kidnapped in Aleppo, Syria, in 2013 and was killed last year. Nisreen Assad Ibrahim Bahar, 25, is the widow of former ISIS leader Abu Sayyaf. Prosecutors said Bahar, also known as Umm Sayyaf, kept Mueller captive and allowed her to be repeatedly raped by ISIS chief Abu Bakr al-Baghdadi. Umm Sayyaf, who is in Iraqi custody on terror-related charges, allegedly told FBI agents last year that she was responsible for Mueller and other hostages while her husband was away. She also “admitted that al-Baghdadi owned Mueller during her captivity,” prosecutors said. If convicted, she could be sentenced to life in prison.