She knew she was allergic to prawns. But Ms Khoo Siew Hong, 60, insisted on eating the shellfish on March 8 as she had consumed some earlier that month without developing any reaction.
This proved to be fatal, for she later went limp and died in hospital.
Delivering his findings yesterday following an inquiry into her death, State Coroner Marvin Bay said her death was a "truly unfortunate misadventure".
He said Ms Khoo, who was unemployed and moved around in a wheelchair, lived with her sister and two helpers - Ms Rosemarie Bastareche and Madam Ten Ah Boh - in a flat in Lorong 3 Geylang.
On March 4, all four women went to Shin Yeh Restaurant in Liang Court shopping mall for lunch, where Ms Khoo ate some prawn dumplings.
She was at home at around noon four days later when she asked to eat some prawns that her helpers had prepared for laksa. They obliged and gave her two pieces.
About 2 1/2 hours later, Ms Khoo complained of itchiness.
Ms Bastareche gave her an antihistamine tablet for an allergic reaction to prawns, which Tan Tock Seng Hospital (TTSH) had prescribed to Ms Khoo.
Coroner Bay said: "About five minutes later, Ms Bastareche noticed Ms Khoo's face started to develop a rash and swelling, and took a damp towel to wipe Ms Khoo's face.
"Ms Bastareche helped Ms Khoo to recline, but she noticed that the rash had increased in intensity...
"After 20 minutes, Ms Khoo complained of breathlessness and Ms Bastareche took medicated oil to apply on her nostrils to aid her breathing."
The helper quickly alerted Madam Ten and the Singapore Civil Defence Force (SCDF) when Ms Khoo went limp shortly after.
An SCDF officer guided Ms Bastareche over the phone as she performed cardiopulmonary resuscitation (CPR) on Ms Khoo until paramedics arrived at 3.40pm.
She was unconscious when they rushed her to TTSH. CPR was continued and 12 doses of adrenaline were administered.
The hospital told Ms Khoo's sister that her prognosis was poor.
After the woman contacted their family members, a decision was made to take her off the ventilator.
Ms Khoo was pronounced dead at around 9.50pm that day.
A forensic pathologist later found that she died of anaphylaxis - a severe allergic reaction - compatible with food allergy.
An autopsy revealed that there was an accumulation of fluid in her larynx, which is consistent with an allergic reaction. Her lungs were also found to be congested.
Yesterday, Coroner Bay said that persons susceptible to shellfish allergies can take certain precautions.
He said: "The only absolute way to prevent shellfish allergy is to avoid all shellfish and all products that contain shellfish. "