Just thinking, apropos of the thread subject, that due to media coverage this lady has already been found 'guilty' by the court of public opinion and media sensation.
It reminds me of that other Australian very high profile 'no smoke without fire' murder case, that occurred under bizarre and unusual circumstances - it was 'known' in 1980 that dingoes don't attack or carry off human infants. Later developments proved that this was in fact the most likely reason for baby Azaria's disappearance.
So, in interests of balance, maybe death cap fungi did get into a dish unintentionally, or some other unknown issue made family members deathly ill?