KUALA LUMPUR, Malaysia -- An Australian woman accused of drug trafficking in Malaysia was sentenced to death by hanging after an appeals court on Thursday overturned a lower court's acquittal, her lawyer said. Maria Elvira Pinto Exposto was exonerated by the High Court last December on grounds that she didn't know there were 1.5 kilograms of crystal methamphetamine in her bag when she was arrested in December 2014 at Kuala Lumpur's international airport. The prosecution appealed.

Exposto, a 54-year-old mother of four from Sydney and also a grandmother, had arrived from Shanghai and was to catch a connecting flight to Melbourne when she was detained in Malaysia. The drugs were discovered when she put two bags through the security scanner when exiting the airport.

Exposto had said she went to Shanghai to meet a U.S. serviceman with whom she had an online romance, and had been asked to carry a bag full of clothes. She said she was unaware that the bag also contained drugs.

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BBC News reports the judge had called her "naive", but added that her "feelings of love...[had] overcome everything."

Exposto's lawyer, Tania Scivetti, said a three-member appeals court "found there was merit" in the prosecution's appeal, though it didn't say on what grounds. She said Exposto was shocked but calm.

"It's disappointing as there was clear evidence that she was the victim of an Internet romance scam. She was a drug mule," Scivetti told The Associated Press, adding that they have appealed to Malaysia's top court.

Malaysia has a mandatory death sentence for anyone found guilty of carrying more than 50 grams of a prohibited drug.

After her acquittal in December, Scivetti said Exposto was immediately arrested by immigration officials as her visa has expired. Following the prosecution's appeal, she remained in custody because she couldn't afford to pay bail.

Australian Foreign Minister Julia Bishop said her government was aware of Exposto's right to appeal.

"Australia opposes the death penalty in all circumstances for all people," Bishop said in a statement.

Diplomatic relations between the two countries chilled for years after Malaysia hanged two Australians in 1986 for heroin trafficking, a move that then Australian Prime Minister Bob Hawke denounced as a "barbaric act."

Despite the backlash, Malaysia hanged another Australian heroin smuggler in 1993. Australia responded with a statement expressing the government's deep regret and sadness.