TROUBLED tourist Samantha Azzopardi is flying home to Australia after an Irish court found she isn't suffering a serious mental illness despite being "vulnerable".

Ms Azzopardi was found in a distressed state on a Dublin street almost a month ago and police initially feared she was a teenage victim of human trafficking.

But she was finally identified this week after an international appeal.

It was subsequently revealed that Ms Azzopardi, who is aged 25 and originally from Sydney, was known to Australian police, had used false identities and been found guilty of deception.

She was escorted by police to Dublin airport on Thursday night local time (Friday morning AEDT) and is expected to arrive in Australia at the weekend.

"Samantha Azzopardi is this evening being returned to her native Australia," a police spokesman said in a statement.

"In consultation with all of the relevant authorities (we) have facilitated Samantha Azzopardi's repatriation with a view to reuniting her with her family and the authorities."

Her departure was shrouded in secrecy, with authorities refusing to discuss her whereabouts until she was in the air.

There was pressure in Ireland for the Australian to be charged with wasting police resources.

It reportedly cost the state more than 250,000 euros ($A357,000) to identify Ms Azzopardi.

Ireland's High Court heard on Thursday that, while the tourist suffers from a condition that makes her "vulnerable", she wasn't so ill she should be detained under the country's Mental Health Act.

A court order that had kept her in hospital lapsed just before midday and police announced she was flying home hours later.

"She is not detainable under the Mental Health Act ... the legal proceedings are at an end," said Gerard O'Brien, a lawyer for the guardian appointed when it was thought Ms Azzopardi was a teenager.

Psychiatrist Brendan Kelly assessed Ms Azzopardi on Wednesday evening and prepared a "fulsome report", the court heard.

It was Dr Kelly's view that Ms Azzopardi does not suffer from a disorder that allows her to be detained against her will.

During her weeks in care, the Australian had threatened a "hunger and thirst strike", Justice George Birmingham revealed.

He said the twists in the case had come "as a shock to everybody and as a surprise".

"But the case has now run its course," the judge said.

The Irish Independent reported police originally believed Ms Azzopardi was only 14 or 15 years old because she weighed just 40kg.

It's thought Ms Azzopardi was staying with her mother's former boyfriend Joe Brennan in Tipperary before she was found.

Local media turned on the young Australian in recent days.

The Independent said authorities had been "taken in by a Walter Mitty-like con artist".

Originally published as Mystery Australian woman leaves Ireland