"She is getting better every day. She is moving her eyes to follow instructions," her uncle André van Breda said after a memorial service in Pretoria on Thursday.
'What the doctors and nurses have done is a miracle'
The Van Breda family were attacked in their home in the De Zalze Golf Estate last month. The 16-year-old's father Martin van Breda, 55, his wife Theresa, 54, and older brother Rudi, 22, were killed. Her other brother Henri, 20, survived.
"What the doctors and nurses have done is a miracle," André said. "What is happening there is part of God's work. Her movements are getting better. She can communicate with her eyes, by blinking.
"Nurses have put up pictures of the family on various holidays and are showering her with love. We are praying that God makes her healthy again. We are asking everyone to pray for her."
Marli was critically injured and remained in hospital. Emergency medical services spokesman Robert Daniels said previously that Marli had an axe wound to the head and her jugular vein had been severed.
Beeld on Friday quoted Van Breda as saying Henri, who was receiving a lot of support and was traumatised, had a legal team.
"Henry's support structure, his legal team, everybody, is supporting him."