The woman was brought to Sydney last month after requesting an abortion, before a government-chartered plane flew her back to Nauru.
The federal government said the decision to return Abyan (not her real name) to Nauru was her own, but her lawyer and refugee advocates disputed that account.
They say the government flew her out of the country to thwart a court injunction that might have allowed her to stay.
Immigration Minister Peter Dutton said Abyan is now back in Australia.
"She is receiving medical attention and as we will do what is in her best interests," she told ABC's Insiders program.
"Her doctors, specialists spoke with her, recommended that she come to Australia, and we've accommodated that. And she is receiving medical attention."
