Shamima Begum fled east London at the age of 15 to travel to Syria to marry an IS fighter in 2015, at a time when the group's online recruitment programme was luring many impressionable young people to its self-proclaimed caliphate.
Ms Begum, now 19, resurfaced recently at a refugee camp in Syria and told reporters she wants to come home with her new baby, but her apparent lack of remorse has triggered criticism in the UK and her family has expressed its shock at her lack of repentance.
She married a Dutch man who wants to take her to the Netherlands with their newborn son.
British Home Secretary Sajid Javid has revoked her citizenship, despite saying he would not make a decision that would render a person stateless.
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Her family has insisted she is not a dual citizen, and the case is pending in the courts.
Ms Begum's father Ahmed Ali told the Associated Press in an interview in his Bangladeshi village that he would still request that the British Government allow his daughter to return.
"My child was only 15 years old when she fled, she was immature," said Mr Ali, who lives in the north-eastern Bangladeshi district of Sunamganj with his second wife.
"I would ask the British Government not to cancel her citizenship, to return her citizenship, and if she is guilty, bring her back to Britain and give her punishment there," he said.
Mr Ali, 60, said he moved to England in 1975 and returned to his village in Bangladesh in 1990 to marry his first wife, Asma Begum.
The couple, who returned to England, have four daughters, with Shamima the youngest.
He later returned to Bangladesh and got married for a second time. Most recently, he went to Bangladesh two months ago to escape the UK winter.
Mr Ali criticised UK authorities for failing to properly deal with the issue of students who have fled to join IS.
"One girl went there a month ago, most likely a month ago. The British Government should have been alarmed about the matter, and they should have also inquired at the school to find out how she fled, since she was a student," he said.
"Then a month later, three more students fled. The authorities should investigate at the school why these students fled. They were not adults.
"The British immigration system is very informed, the most informed system in the world. I always say how did (Shamima) get there using another one's passport? She doesn't even have her own passport. These matters should be investigated as well."
His daughter's husband, Yago Riedijk, 27, told the BBC this month from a Kurdish-run detention centre that he met Ms Begum within days of her arrival in Syria when she was 15. He said the marriage was "her own choice".
Asked if marrying a 15-year-old was appropriate, he said: "To be honest, when my friend came and said there was a girl who was interested in marriage, I wasn't that interested because of her age, but I accepted the offer anyway."
He said that while he fought for IS, he now rejects the group and tried to leave it.
While it is unclear if Ms Begum has committed a crime, her comments - and those of her husband - throw into sharp relief larger questions about how Western societies will deal with others who joined IS but want to return to their home countries now the extremist group is on the verge of collapse.