A spokesman for the Ministry of the Attorney General says they will add themselves as a party to the case and make a joint submission to court with the involved parties.
The deadline to file an appeal has been extended several times while the government worked with the family to find "the most respectful and effective" ways to provide health care for the girl.
The girl, whose name cannot be revealed due to a publication ban, was receiving chemo last September before her mother removed her and took her to Florida for alternative therapy.
That decision prompted the McMaster Children's Hospital in Hamilton to take the Brant Family and Children's Services to court, seeking to have the child apprehended and placed back into chemotherapy.
A judge dismissed the hospital's application in November, saying traditional aboriginal treatments were in existence before First Nations communities were in contact with Europeans, and were consequently entitled to special protection in Canada.
The girl's mother said in February at a conference on aboriginal medicine that she has met with provincial government officials and they have been "respectful and compassionate."