Fresh details of Kayla Mueller's days as an ISIS captive are revealed in an ABC 20/20 report airing Friday night, and they highlight both the horror of her circumstances and her amazing strength. Four former hostages, including three women who shared a cell with the young American in 2014, say they were inspired by her optimism, humor, and the strength she drew from her Christian faith. "She was always considerate of others, even though she herself was in a very difficult situation," says Frida Saide, a former captive from Sweden. "She was always concerned for other prisoners." Mueller, who was repeatedly raped by ISIS leader Abu Bakr al-Baghdadi, died in captivity last year.
Former hostage Daniel Rye Ottosen from Denmark describes how she stood up to the notorious "Beatles" group of guards, including "Jihadi John." "One of the Beatles started to say, 'Oh, this is Kayla, and she has been held all by herself. And she is much stronger than you guys. And she's much smarter. She converted to Islam.' And then she was like, 'No, I didn't.'" People notes that the ABC report will also include a chilling "proof of life" video sent to Mueller's parents after her capture in 2013. "I've been here too long and I've been very sick," she says. "It's very terrifying here." ABC also spoke to two Yazidi girls who say that to ensure their safety, Mueller chose not to escape with them. (Read more Kayla Mueller stories.)