WESTERN CANADA — As a teenager, S. was grieving the killing of her brother, facing Islamophobic harassment and searching for a stronger connection to her faith. In 2014, at barely 19, she left Canada for Turkey and was smuggled into Syria, believing she was joining a Muslim community where she could practice her religion freely. Instead, she was taken to Raqqa, then the center of the Islamic State’s self-declared caliphate. She saw evidence of the group’s brutality almost immediately, including severed heads displayed in public, she recalled. S., who was born in Pakistan to Somali parents and raised in Canada from age 2, asked that her full name and home city not be published because of the risks associated with her past. Her account describes a path from religious devotion and alienation to coercion, violence and, ultimately, cooperation with authorities working against ISIS. Before leaving Canada, S. had enrolled in a religious boarding school in eastern Canada, where she befriended a woman who had joined al-Shabab, an al-Qaida-linked militant group. The woman encouraged her to leave the West. At the same time, Canadian intelligence officials began contacting S. about her associations, a process she said left her frightened and increasingly isolated. After her parents asked her to leave home amid government inquiries, the woman arranged her travel to Turkey. Smugglers then transported S. and other recruits into Syria, where armed men confiscated their passports and sent them onward to Raqqa. At a guesthouse near the Euphrates River, ISIS supporters pressured her to marry. She initially refused several proposed husbands and was confined, denied basic necessities and threatened with violence. She eventually escaped through a back door with another Canadian woman who was pregnant. S. later married a Moroccan man who had helped care for the pregnant woman. She said she accepted the marriage partly because it offered a way out of the guesthouse. The couple had a daughter, but the marriage became abusive. When S. sought a divorce, an ISIS judge told her she was not a free woman and had to obey her husband, she said. As U.S.-backed Kurdish forces and ISIS fought for control of Raqqa, S. fled with her husband and young daughter. She gave birth while a hospital was under bombardment and later struggled to feed her toddler as the family moved through the war zone. She described people eating grass and said her daughter became malnourished. The family eventually reached Baghuz, the site of ISIS’ final territorial stand in Syria. When Kurdish forces offered women and children the chance to surrender, S. left with her daughter. Her husband stayed behind to fight. They were taken to al-Hol, a sprawling detention camp in northeastern Syria that held tens of thousands of people connected to ISIS, many of them women and children. S. said she feared children in the camp were being indoctrinated and recruited into the group’s next generation. She began secretly working with Kurdish authorities, wearing military clothing and covering her face at night. Her information helped identify children held in the camp, including Aminah, an American child whose parents had died in the fighting. S. pointed out the tent where the child was being kept, allowing Kurdish forces to remove her. Former U.S. Ambassador Peter Galbraith, who was working with medical, diplomatic and law-enforcement officials to locate ISIS-affiliated children, said S. initially sought an agreement that her cooperation would secure her release. He declined to make such a deal, he said, but she provided information anyway. The work was dangerous. S. said women in the camp would have tried to kill her if they discovered she was cooperating with Kurdish or Western officials. After her role became known, she was taken to a Kurdish prison and held in solitary confinement with her daughter for several weeks. Galbraith later helped arrange for S.’s daughter to leave Syria for the Kurdish-controlled city of Irbil in Iraq. The girl’s aunt then brought her to Canada. S. said she had promised her daughter that she would follow, but it took another year for her to return home. S. is now 35 and works in skin care. She said she has helped Canadian and U.S. authorities identify ISIS fighters and supporters, provide evidence used in prosecutions and locate children separated from their families. She does not discuss her past with friends or co-workers. Her daughter, now in fourth grade, remembers fragments of life in Syria, including living in tents and friends she left behind. She does not understand the full history. Today, she says she wants to become a scientist or an astronaut. S. acknowledges that some people believe she should not have been permitted to return to Canada. She maintains that she no longer has ties to ISIS and that her cooperation with authorities has helped protect others. Her story also underscores the difficult choices facing governments dealing with citizens who joined extremist groups: how to weigh security and accountability against the rights and safety of children caught in war.