Dr. Atchison announced on her Twitter account Thursday the unexpected death of her 26-year-old daughter, Caillin.
According to a now-deleted Twitter post, Caillin died on Wednesday while in her sleep.
"The light in our life has gone out. My beautiful and only daughter died yesterday," Dr. Atchison tweeted.
"She never woke up. It was so utterly unexpected and my husband and my hearts are shattered. I really don't know what to do," Atchison added.
There is still no information on the cause of Caillin's death.
Dr. Atchison became the public spokesperson for nurses and hospital staff during the Covid-19 pandemic, according to the Daily Mail.
She was critical of South Australia easing its border closure on November 23, warning the reopening would place further strain on the health system.
She also presented the latest report into South Australia's healthcare system that revealed a crippling shortage of healthcare staff and beds in hospitals.