There was little reaction from Kuka as she was found guilty of manslaughter.
A date for the five to be sentenced will be set later.
Over the past month the court heard details of abuse suffered by Nia in the months before her death.
Wiremu Curtis, who had been in a relationship with Kuka, 35, and his brother Michael Curtis, 22, had pleaded not guilty to murder.
Kuka, Michael Curtis's partner Kemp, 18, and Nia's cousin Pearson, 20, had pleaded not guilty to manslaughter.
All but Kuka were also accused of multiple, less serious offences.
The Crown alleged Nia suffered months of abuse at the hands of the accused but it was the Curtis brothers who delivered the fatal attack, kicking her in the head on the evening of July 20 last year.
The five last week declined to give evidence in their own defence.
- NZ HERALD STAFF, with NEWSTALK ZB