Shamima Begum, who travelled to Syria in 2015 and now wants to return to Britain after giving birth in a refugee camp in Syria last week, said the order was "unjust".
"I am a bit shocked," she told ITV News after learning of the move, which was announced in a letter Tuesday from the British government to her mother in London.
"It's a bit upsetting and frustrating. I feel like it's a bit unjust on me and my son."
She said an "option" could be to apply for citizenship in The Netherlands, where her husband and the father of her newborn child -- an IS fighter believed to be held by Kurdish forces in Syria -- is from and has relatives.
"Maybe I can ask for citizenship in Holland," Begum added. "If he gets sent back to prison in Holland I can just wait for him while he is in prison."
- 'Children should not suffer' -
Begum's fate has stirred controversy since she and two friends fled her east London home to join the terror network four years ago when she was aged 15.
The case highlights a dilemma facing many European countries, divided over whether to allow jihadists and IS sympathisers home to face prosecution or bar them over security concerns as the so-called "caliphate" crumbles.
Britain's Home Office said it did not discuss individual cases when asked about Begum.
Interior minister Sajid Javid told lawmakers Wednesday that revoking citizenship was "a powerful tool" not used lightly.
"But when someone turns their back on (our) fundamental values and supports terror they don't have an automatic right to return to the UK," he said.
However Javid hinted that Begum's newborn son could be treated differently.
"Children should not suffer, so if a parent does lose their British citizenship it does not affect the rights of their child," the minister said.
Begum gave birth to her third child at the weekend, and appealed to British authorities to show "compassion" by allowing her to raise the baby in Britain -- while expressing no regret over having joined IS.
- 'All legal avenues' -
In the ministry's letter sent to Begum's mother, it said the teen had the right to appeal the order.
Tasnime Akunjee, a lawyer for her family, said it was disappointed with the move and "considering all legal avenues to challenge this decision".
Begum, who is of Bangladeshi heritage, was born in Britain, has never had a Bangladeshi passport and is not a dual citizen, according to Akunjee.
The Home Office reportedly believes that she is entitled to claim citizenship in the south Asian country.
Chiranjiv Sarker, head of the consular wing and dual nationality issues at Bangladesh's foreign ministry, told AFP it was aware of the case but had not received any contact from the family.
"So far none of her family members (has) approached us," he said. "What I learn from newspapers is that Shamima was trying to return to Britain."
He added that, if approached, the ministry would need to try to verify Begum's Bangladeshi heritage to assess any possible eligibility for citizenship.
- Trump call rebuffed -
Begum is currently in a refugee camp in northeast Syria where she fled to escape fighting in the east of the country along with hundreds of other people with links to IS.
She said she had previously given birth to two other children after marrying in Syria. Both children are said to have died, apparently from illness and malnutrition.
Begum fled Britain with Kadiza Sultana, who has since been reported killed, and Amira Abase.
Begum said in recent media interviews that Abase had stayed in a village where IS fighters were making a final stand against US-backed forces.
European countries have been grappling with what to do with foreign fighters detained in Syria by the Kurdish-led Syrian Democratic Forces, who have warned they may not be able to guard their jails once US troops leave.
The British government on Monday rebuffed US President Donald Trump's call for European allies to take back hundreds of alleged jihadists captured in the war-ravaged country.
Prime Minister Theresa May's spokesman said the fighters should instead face justice in places where they committed their crimes.