Eight candles were lit to mark each birthday the toddler has missed since her death in 2007.
There was a cake, sausage sizzle and a chance for the community to talk about the future.
"My 10-year-old asked me what this was for," said Koutu mum Pare Richards.
"[Nia] would have been around his age now. She could have been here to see what Koutu is doing. It's important to have this ceremony for Nia and others to show we don't think it's okay for anyone to live that way. It's another step in what we've been doing so far to reinforce the other things we've been doing."
There was plenty of positive reinforcement, but there was also reflection on the past attitudes towards family violence.
Mr Flavell said it was a great thing that the community was standing up. "Nia will forever be in our psyche. She's left us but she's in our hearts.
"Any initiative addressing domestic violence we have to support. The good thing is people are doing what they can. It's bringing it forward in a positive way."
Mr Horne told the crowd Nia's death still haunted the officers who were involved in the investigation. The rally was another opportunity to keep the conversation going that family violence was not acceptable.
He likened it to the drink-driving culture, which had changed from being condoned to now being unacceptable among peers. "People need to be encouraged and know there's hope. Their past doesn't have to be their future. Across Rotorua in particular there's been a growing momentum for change."
Mrs Chadwick, who brought her family up in Koutu, said the event was about letting go.
"It's been eight years and there's a new growth here, a linked-up community. We're proud of what Koutu is achieving. It's a community rebuilding."