The deadline for Sandiford - who has two sons in their 20s and a granddaughter aged two - to file an application for clemency passed five months ago and she now fears she will face a firing squad at the same time as the Australians.
Speaking from Bali's Kerobokan Prison, Sandiford told her sister Hilary Parsons in a phone conversation: "If I sign the letter, am I signing my own death warrant? Am I saying, 'Go ahead and shoot me?' The letter is in Indonesian so I won't even know what it says."
Sandiford has no legal representation after the British Government refused to fund a lawyer for her, and yesterday she wrote to Foreign Secretary Philip Hammond asking him to reverse his decision not to pay the £38,000 cost of another appeal against her sentence.
British judges previously ruled that she should be considered an "exceptional" case after she was sentenced to death while the ringleaders of the same drug-smuggling gang escaped with jail terms.
Former legal secretary Sandiford, who has no previous criminal convictions, was caught smuggling cocaine worth £1.6 million from Thailand to Bali in 2012. Her sentence was upheld on appeal. She claims she was forced to act as a drugs mule by a syndicate who threatened the lives of her sons in England.
The other suspected syndicate members - Julian Ponder, 45, Paul Beales, 41, and Rachel Dougall, 41 - were sentenced to six years, four years and one year respectively.
Five Supreme Court judges in London last July called on Hammond to "urgently'' consider providing legal assistance to Sandiford, concluding that the Indonesian courts had ignored substantial mitigating factors in her case.
Hammond wrote to Sandiford in a letter dated August 11 dismissing the judges' suggestion and saying features of her case were "regrettably present in many other cases in which British nationals have been sentenced to death overseas''.
- Daily Mail