“Mediclinic Southern Africa can confirm that Miss van Breda’s condition remains unchanged; she is still critical but stable,” spokeswoman Carla Hanekom said in a statement.
“She is being constantly monitored and no visitors are allowed at this stage.”
The girl was initially treated at Stellenbosch Medi-Clinic in the Western Cape and had since been moved to a nearby medi-clinic, she said.
The Cape Argus identified her as Marli van Breda on Wednesday.
Emergency medical services spokesman Robert Daniels said he could only comment on the wounds of the patient they treated, and not those who were killed.
“The patient [Marli] had an axe wound to the head. The jugular was severed,” he said at the time.
The family were attacked in their home in the De Zalze Golf Estate in the early hours of Tuesday morning. The teenager’s father Martin van Breda, 55, his wife Teresa, 54, and older brother Rudi, 22, were killed. Her other brother Henri, 20, survived, the newspaper reported.
Lt-Col Andre Traut said a 16-year-old daughter and 20-year-old son were injured and admitted to a nearby hospital.
No arrests had been made and no one had been taken in for questioning by Wednesday morning, said Col Tembinkosi Kinana.
“The identities of the family have not yet been confirmed at this stage. Police investigations are continuing,” Kinana said.
He declined to disclose how the family was killed, or a possible motive.