Shamima Begum, who left the UK for Syria as a teenager to join the Islamic State group, was a victim of human trafficking for sexual exploitation purposes, a tribunal has been told.
Ms Begum travelled to Syria in 2015, with her citizenship stripped on national security grounds in 2019.
A five-day immigration hearing is considering an attempt to challenge the removal of her UK citizenship.
The Home Office insists she continues to pose a threat to national security.
The case is being heard at the Special Immigration Appeals Commission (SIAC), which has similar standing to the High Court, and can hear national security evidence in secret if necessary.
Lawyers for Ms Begum, now 23, told the court that a decision by then-Home Secretary Sajid Javid to remove her British citizenship was unlawful, as it did not consider whether she had been a child victim of trafficking.
She remains in a camp controlled by armed guards in northern Syria, nearly eight years after running away from home aged 15 alongside two other east London schoolgirls - Kadiza Sultana, 16, and 15-year-old Amira Abase.
Ms Sultana is believed to have been killed in a Russian air strike in Syria, according to her family's solicitor.
The whereabouts of Ms Abase are unknown, but Ms Begum previously said in a 2019 interview that she had heard she might still be alive.
In August, a BBC News investigation revealed Ms Begum was smuggled into Syria by an intelligence agent who was working for Canada at the time. The Canadian government has said that it will "follow up" on the allegations.
Once in Syria, she married a Dutch recruit and lived under IS rule for more than three years.
In 2019, she was found by the Times newspaper, nine months pregnant, in a Syrian refugee camp. Her baby later died of pneumonia and Ms Begum said she had previously lost two other children.
In an interview with the BBC's I'm Not a Monster podcast in September 2021, Ms Begum said she would regret joining the Islamic State group (referred to as IS, ISIS and ISIL) for the rest of her life and offered to help the UK fight terrorism.
Ms Begum previously said the 2017 Manchester Arena bombing, in which 22 people - some of them children - were killed in a bombing claimed by IS, was similar to military strikes on IS strongholds and called the terror attack "retaliation".
BDST: 1018 HRS, NOV 22, 2022