Ms Begum, who left the UK with two other east London schoolgirls at the age of 15 in February 2015, is challenging the Home Office's decision to remove her British citizenship.
The 21-year-old asked a specialist tribunal to consider whether she was a victim of trafficking when she travelled to Syria.
Her British citizenship was revoked on national security grounds shortly after she was found in a Syrian refugee camp in February 2019. She was nine months pregnant at the time.
Ms Begum's lawyers told the Special Immigration Appeals Commission at a hearing on Friday that the Home Office had a legal duty to investigate whether Ms Begum was a victim of trafficking when her citizenship was revoked.
Samantha Knights said “the counter-terrorism unit had suspicions of coercion and control” when Ms Begum left the UK.
She argued this “gives rise to the need to investigate the issue of trafficking”.
In written submissions, Ms Begum’s lawyers said the Home Office failed to consider whether she was “a child trafficked to, and remaining in, Syria for the purposes of sexual exploitation and forced marriage”.
Her lawyers argued the removal of her British citizenship would make her “de-facto stateless”.
Ms Begum is currently at the al-Roj camp in northern Syria, which is run by the Syrian Democrat Forces (SDF).
Ms Knights said conditions there are “dire” and "unsafe".
She said: “Physical violence is common and psychological trauma is endemic.”
She asked the Special Immigration Appeals Commission to consider Ms Begum's proposed new grounds of appeal in November.
But a lawyer representing the Home Office argued the claim that Ms Begum was trafficked is "entirely speculative".
David Blundell, argued in written submissions: “It is significant that the allegation is not that Ms Begum was trafficked, but rather that she ‘may have been’ trafficked.
“Ms Begum herself has never stated that she has been trafficked, despite having given numerous media interviews and provided instructions to her solicitors on a number of matters.
“The absence of a claim that she has in fact been trafficked means this ground proceeds on an uncertain factual basis."
Mr Blundell added: “Although Ms Begum focuses on the fact that she left at 15, she ignores the fact that she remained in Isil (Islamic State of Iraq and the Levant) territory in Syria for a considerable period of time as an adult, only leaving when the so-called caliphate fell.
“It was at that stage, not when she was a child, that the deprivation decision was taken.”
The Home Office said Ms Begum’s case should be put on hold until a separate similar case has concluded.
The commission on Friday also heard the cases of three other women who have all had their British citizenship revoked on the grounds of national security.
Mr Justice Jay said he would aim to give his ruling in the last week of June.