An Australian woman has been sentenced to death in Malaysia after a court of appeal found her guilty of smuggling crystal meth.

Maria Elvira Pinto Exposto, 54, was found with more than one kilo of crystal methamphetamine on her at Kuala Lumpur airport in 2014, before she was due to board a flight to Melbourne.

The drugs were sewn into the lining of a bag that had been given to her by her boyfriend, whom she had met online. He claimed to be Capt Daniel Smith of the US special forces.

Exposto was acquitted of the crime in December 2017 when the judge ruled she had been groomed for two years by the man, with whom she had fallen in love, and been scammed into carrying the rucksack, which had been given to her in Shanghai.

Exposto, from Sydney, said she did not know the drugs were there, and had voluntarily put the bag through the airport scanner during a stopover in Kuala Lumpur.

However, the prosecutor had filed an appeal at the beginning of this year, and the courts have now overturned Exposto’s acquittal, finding her guilty of a 39B drug trafficking charge, which carries a mandatory death sentence by hanging.

“It does not make sense that she was just helping someone she did not know carry something,” said the prosecution in their appeal. “There were many opportunities for Maria to scrutinise the bag, which was given to her by someone she met only hours earlier. She should have been suspicious.”

In a unanimous verdict, all three court of appeal judges ruled that the merits of the appeal were valid and found Exposto guilty, with the only sentence under law being death by hanging.

Exposto’s lawyer Shafee Abdullah said he was totally shocked by the reversal of the judgment, which he described as perverse. He said they would be appealing in the federal court.

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