While there, Shamima Begum married an IS fighter and had three children, none of whom survived.
A judgement is expected Friday in the appeal case of a woman who lost her British citizenship after leaving as a teenager to marry an Islamic State group fighter.
Shamima Begum, 24, took her case against the revocation of her citizenship to the Court of Appeal in London in October last year.
Her lawyer told the court that the Home Office had failed to consider its legal duties to Begum as a potential victim of trafficking.
Begum, whose family is of Bangladeshi origin, was 15 years old when she left her east London home for Syria with two school friends in 2015.
While there, she married an IS fighter and had three children, none of whom survived.
In February 2019, Begum said she was left stateless when Britain's interior minister at the time, Sajid Javid, revoked her British citizenship on national security grounds after she was found in a Syrian refugee camp.
A UK tribunal ruled in 2020 that she was not stateless because she was "a citizen of Bangladesh by descent" when the decision was made, by virtue of her Bangladeshi mother.
Last year, Begum lost a challenge against the decision at the Special Immigration Appeals Commission (SIAC).
The SIAC said that while there was a "credible suspicion that Begum was recruited, transferred and then harboured for the purpose of sexual exploitation", this did not prevent Javid from removing her citizenship.
The ruling meant that Begum could not return to the UK from her current home, a refugee camp in northern Syria.
Lawyers for the Home Office have argued that SIAC's conclusion was correct.
Begum is one of hundreds of Europeans whose fate has challenged governments following the 2019 collapse of the Islamist extremists' self-styled caliphate.
Begum's lawyer told the SIAC hearing that her client had been "influenced" along with her friends by a "determined and effective" IS group "propaganda machine".
Around 900 people are estimated to have travelled from Britain to Syria and Iraq to join the IS group. Of those, around 150 are believed to have been stripped of their citizenship, according to government figures.
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