It's unclear exactly how long after ingestion that the woman and her daughter became ill or how long after they died.
Allergic reaction sounds like a furphy, more likely that the restaurant's rat poison was mistaken for an ingredient in the dish.
Allergic reactions of a life threatening nature will have a rapid onset with swelling of the respiratory passages - oedema, not vomiting.
Food poisoning rarely kills and is treated with antibiotics. Can't imagine you would die that fast as death is more likely to occur from fluid depletion, rather than the bacteria itself.
If they were my family I would be requesting that an Australian autopsy also be done with toxicology testing being paramount and preferably at an Australian facility.
