The youngest daughter of the Biloela family being held in detention on Christmas Island is being medically evacuated to Perth with a suspected blood infection.
Tharnicaa, who is aged three, is flying with her mother Priya, the family and refugee advocates said in a statement on Monday afternoon.
They say Tharnicaa has been unwell for 10 days and might have septicaemia.
"I am feeling very scared and worried for my little girl," Priya said.
"She has been sick for many days, it took a long time for her to get to the hospital.
"She is already asking for her papa, it is going to be very hard being away from her Dad and sister. It is very hard for our family to be separated when our daughter is sick."
Their flight is expected to arrive in Perth around 5pm local time.
Tharnicaa had been feeling unwell for 10 days with vomiting, diarrhoea, dizziness, and a temperature of more than 40 degrees.
Detention centre staff didn't take Tharnicaa to the hospital until Sunday, despite ongoing requests from her mother, advocates say.
Priya, Nades and their two Australian-born daughters, Tharnicaa and six-year-old Kopika, have been held on Christmas Island since August 2019 as the government tries to deport them to Sri Lanka, despite a community campaign to let them stay.
They were removed from their home in the rural Queensland town of Biloela and placed into immigration detention in 2018.
The federal government has spent more than $6 million keeping the family in detention for the past three years.
Family lawyer Carina Ford said Tharnicaa's condition had gotten significantly worse over the weekend.
She said the family had received medical reports indicating the two girls were suffering from both physical and mental health issues.
"I think their day-to-day life is getting harder and harder, and there is no doubt that there is a greater impact on the children," she told ABC News.
The Department of Home Affairs has been contacted for comment.
Labor Senator Kristina Keneally expressed concern for Tharnicaa and her family.
"A medical emergency and family separation is the last thing they need," she said.
"This family should not be in detention. They should be in their community in Biloela."
