Patterson's nine-year-old daughter described her mother's sickness in a recorded police interview played to the Victorian Supreme Court jury on Thursday.
The girl told police her mother invited Don and Gail Patterson, and Gail's sister Heather and her husband Ian Wilkinson, over for lunch on July 29, 2023, to talk about "adult stuff".
The next morning, Patterson began feeling unwell and used the bathroom 10 times over the course of the day, the girl told police.
"She just needed to go to the toilet a lot and she felt sick in her gut," the child said.
Patterson presented to hospital on the morning of July 31, where the rest of her lunch guests were being treated for death-cap mushroom poisoning.
Don, Gail and Heather died in the days after the poisoned lunch, while Ian survived.
Patterson has pleaded not guilty to three counts of murder and one count of attempted murder and is on trial in Morwell in regional Victoria.
Registered nurse Cindy Munro told the court she assessed Patterson in hospital about noon on July 31 after being involved in the treatment of Ian and Heather earlier that morning.
Patterson reported having nausea and diarrhoea but the nurse said her appearance was different from the other lunch guests.
"She didn't look unwell like Heather and Ian," Ms Munro told the court.
"I recall Ian being so unwell he could barely lift his head off the pillow ... but Erin was sitting up in the bed, in the trolley, and she didn't look unwell to me."
The nurse said Patterson tried to refuse IV fluids and a recommended liver medication but complied after medical staff insisted.
Patterson also advised Ms Munro her children had eaten the lunch leftovers the next day but she had scraped off the mushrooms.
Ms Munro told Patterson the children should come to hospital for assessment but she tried to object, saying she was worried it would stress them out.
"That's when she became quite teary and quite worried," Ms Munro told the jury.
"I did say to her even if she had scraped off mushrooms some could have seeped into the meat and they could be exposed."
Ms Munro organised for an ambulance to transport Patterson to Monash Hospital, where her children were being taken by her estranged husband Simon Patterson.
Paramedic Eleyne Spencer told the court Erin appeared well when they arrived to transport her, and she was calm and chatty throughout the 90-minute journey.
Patterson did not have continuing diarrhoea but she did complain of a severe headache and was given fentanyl because paracetamol would affect the liver medication, Ms Spencer said.
A police officer who retrieved a leftover beef Wellington sample from Patterson's home on the morning of July 31 also gave evidence on Thursday.
Senior Constable Adrian Martinez-Villalobis told the jury Patterson had provided the passcode for the property's gate and instructions on where the leftovers should be.
The beef Wellington leftovers were located in a brown paper Woolworths bag in an outdoor waste bin where Patterson had suggested, the senior constable said.
The officer agreed Patterson had been co-operative with police throughout their search.
The trial before Justice Christopher Beale will continue on Friday.
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