One woman who looked after three British schoolgirls when they joined the terror group said they would "probably die" in the warzone.
"You cannot have a mind of your own, you have to follow their orders," the 22-year-old, who claims to be an Isis defector, told Britain's Sky News.
She described the sophisticated manipulation and radicalisation of young minds on social media.
"IS are not stupid," she said. "They have educated people who know how to deal with [the] psychology of others. They have ways to attract people, especially foreigners. Otherwise young British people wouldn't come and say they will change the flag on Buckingham Palace.
"They have freedom and everything is available. They have no need to come to Syria, but they do."
The Utopian dream promoted by Isis' slick propaganda machine stands in stark contrast to a dire reality now driving attempts by some foreigners to return home.
Among those are relatives of Tara Nettleton, who have asked authorities to allow the repatriation of the Sydney mother and her five children, one of whom is a 7-year-old boy photographed last year holding up a severed head.
His father, jihadist Khaled Sharrouf, is thought to be one of around 100 Australians fighting in Syria and Iraq.
Linford, who heads Victoria Police's Security and Organised Crime Intelligence Unit, said young women were lured by the prospect of a romanticised future under Isis.
"Our intelligence tells us these women are going over there to meet their partners, to marry somebody in an arranged marriage or be pushed into sexual servitude," she said.
"They have told family and friends a story which is not what it seems to be. They say they are going somewhere else or travelling for some other purpose."
