Ms Begum, originally from Bethnal Green, left the UK as a schoolgirl to join Islamic State in Syria and was later stripped of her British citizenship by the British government.
She is fighting to have it reinstated, claiming she was trafficked.
Documentary-maker Andrew Drury, who has spoken to the 23-year-old on several occasions, claimed Begum was a “narcissist” and questioned her remorse.
It comes as her journey to joining ISIS is investigated in a 10-part BBC podcast, I’m Not a Monster.
Ms Begum has consistently claimed she was groomed into joining the terror group as a 15-year-old. She gave birth to three children while in Syria, none of whom have survived.
She told the podcast that she accepts she is viewed “as a danger, as a risk”, but blamed her portrayal in the media.
She said: “I’m just so much more than ISIS and I’m so much more than everything I’ve been through.”
But Mr Dury told the Times newspaper: “She sees herself as a victim now but she told me quite clearly it was her choice to go [to Syria] and she went of her own free will.
“She is a narcissist. She wants to be a somebody. Now she sees herself as a celebrity. Being part of Isis meant she was a somebody and now she’s a somebody again.”
He claimed she was trying to “create a character”, and that she never mentioned a story of being “trafficked or groomed” to him.
The Special Immigration Appeals Commission is set to rule on the loss of her citizenship by May. She currently resides in a Syrian refugee camp.
In November, lawyers for Begum told the commission that she was recruited, groomed and trafficked into Syria before being sexually exploited by an older man.
However, the Home Office alleges she went to Syria knowing the horrors of ISIS, and that even if she had been trafficked she could remain a danger to Britain.
The BBC podcast, which began this month, bills itself as a “definitive narrative on this complex, nuanced and shocking story”.
But some critics have questioned whether Ms Begum should be given a platform.
Tory MP Giles Watling, who sits on the Commons digital, culture, media and sport committee, questioned whether we should “give these people airtime”.
A BBC spokesperson has previously defended the podcast, saying: “This is not a platform for Shamima Begum to give her unchallenged story.
“This is a robust, public interest investigation in which Josh Baker has forensically examined who she really is and what she really did.
“We’d also encourage people to listen to the podcast and make up their own mind."