Earlier this year she lost her legal challenge over the decision to deprive her of her British citizenship.
This week the appeal against the decision began, with Begum's barrister arguing that the Home Office failed to consider that she had been groomed.
Samantha Knights KC said in a written statement: "The appellant’s trafficking was a mandatory, relevant consideration in determining whether it was conducive to the public good and proportionate to deprive her of citizenship but it was not considered by the Home Office."
The appeal comes several months after Sir James Eadie KC, for the department, said that the security services "continue to assess that Ms Begum poses a risk to national security".
As her appeal continues, here’s a timeline of events from her being a straight-A student to being statelessness.
Ms Begum was born to Bangladeshi parents in east London.
Ms Begum, then aged 15, was a pupil at Bethnal Green Academy in east London when she became interested in the terrorist group IS – sometimes known as Islamic State, ISIS or Daesh.
She travelled to Turkey from Gatwick Airport to join the group with her school friends Kadiza Sultana, 16, and Amira Abase, 15.
Despite her family's warnings that Syria was a dangerous place, the teenager crossed the border days later with the help of a Canadian spy named Mohammed al-Rashed.
She said in the Shamima Begum Story BBC podcast series she was told to "pack nice clothes so you can dress nicely for your husband".
Only 10 days after arriving in the city of Raqqa, Ms Begum married a Dutchman named Yago Riedijk, who had converted to Islam.
They had three children: a one-year-old girl, a three-month-old boy and a newborn son. All three have since died from malnourishment or disease.
Ms Begum left Raqqa with her husband but they were split up after she claimed he was arrested for spying and tortured.
An alliance of Syrian and US fighters took Raqqa back from IS control after three years.
Early February 2019
Ms Begum was found in a refugee camp in al-Roj by a Times journalist. She told the reporter it "didn't faze me at all" when she saw her first "severed head" but would "do anything required just to be able to come home".
But the runaway schoolgirl said she did not regret travelling to IS-controlled Syria, saying she had had a "good time".
She gave birth to her third child, Jarrah.
The then-Met Police commissioner Dame Cressida Dick said Ms Begum could expect to be "spoken to" if she returned to the UK.
February 19, 2019
She was stripped of British citizenship after announcing her desire to return to the UK with her then-unborn third child. The decision was deemed permissible under international law only if it did not leave her stateless. Ms Begum described the initial move to revoke her citizenship as "unjust on me and my son".
The home secretary at the time, Sajid Javid, said although he would never leave an individual stateless, his priority was the "safety and security" of the UK.
Mr Javid said he believed her Bangladeshi heritage would make her eligible to live in that country.
Ms Begum’s father, Ahmed Ali, said he did not object to the decision. “If she at least admitted she made a mistake then I would feel sorry for her and other people would feel sorry for her but she does not accept her wrong,” he added.
Jarrah’s death from a lung infection prompted Labour frontbencher Diane Abbott to call the Government "callous and inhumane".
The Begum family started a legal process against Mr Javid’s decision.
Ms Begum was refused "leave to enter" permission to come to the UK for a short time – a decision she appealed against.
Aged 20, she lost her appeal and was prevented from returning to London.
The court of appeal ruled that Ms Begum should be allowed to return to the UK to challenge the Government's decision.
The Government appealed against this ruling, sending the case to the supreme court.
She appealed for forgiveness and said it was “unjustifiable” that IS had killed innocent people.
Her appearance had also changed and she was seen wearing a Nike baseball cap, a grey vest, Casio watch and with her fingernails painted pink.
“I do not believe that one evil justifies another evil. I don’t think that women and children should be killed for other people’s motives and other people’s agendas,” she said.
Ms Begum said there was "no evidence" she was a key player in preparing terrorist acts and was prepared to prove her innocence in court.
She denied the western clothes she was wearing on Good Morning Britain – in stark contrast to the traditional Islamic dress she previously worn – was a publicity stunt.
Before the Special Immigration Appeals Commission (SIAC), Ms Begum’s counsel said: “Without seeking to investigate and determine, still less consider, whether she was a child victim of trafficking and whether there were failures by public authorities in the UK to prevent her being trafficked.”
In the BBC podcast series, she said she understood public anger towards her but insisted she was not a "bad person".
She said she accepted she was viewed "as a danger, as a risk", but blamed her portrayal in the media.
February 22, 2023
Ms Begum lost her appeal in a SIAC court to overturn the Government’s decision to strip her of her British citizenship.
Shamima Begum's appeal against the loss of her British citizenship begins in the court of appeal.
Begum’s team of barristers claim she was a victim of Isis propaganda and was groomed into terrorism.