Nya was one of 77 people to be baptised in the ceremony, and was the youngest to be immersed.
Conference spokesman Lane Vermaas, of Queenstown, said it was rare for someone so young to be baptised by the Jehovah's Witnesses church.
The religion was very particular about who was baptised.
Only those who had studied the Bible enough to be able to make their own decision about ''following God's will'' could be baptised, he said.
''So very few children get baptised. We don't believe in baptising babies.
"Nya has gone through an extended period of Bible study, and she has been asked a series of questions to make sure her decision to get baptised is her own decision.''
The baptisms were witnessed by more than 5200 people at the stadium.
