Since beginning work with Sia, Ziegler has starred in videos for Sia's songs "Chandelier" (which has over 1.7 billion views), "Elastic Heart", "Big Girls Cry", "Cheap Thrills", "The Greatest" and more.
Maddie was eight when she started appearing in Lifetime's reality series Dance Moms in 2011.
But following concerns about the relationship raised by Guardian writer Bonnie Malkin, who questioned whether Sia should be foisting onto a young girl the fame she so publicly despises, Sia has explained her decision-making process.
Malkin called into question the staging of Sia's latest tour after watching her perform in Sydney.
The column asked whether the spotlight-shy artist was exposing a child to the same fame she sought to avoid, writing that "the grown-up who has seen what fame can do and fears it has, perhaps unwittingly, handed it over to the child instead".
Sia has now responded to the column on Twitter. It's a conversation we should all be having. "Not just myself but all directors, stage parents and agents with their children, clients, charges", Sia wrote on Twitter.
Sia said that the teenage dancer was "already famous" before she discovered her but admits she has expanded her exposure. I feel very protective of her and my goal is to empower her in whatever choices she makes. Some would argue a teenager can't or shouldn't be charged with making sound choices for themselves and so I do try to choose the best for her always. "But I think this is an important conversation", the Australian singer continued.
Posing on a beach in front of Rangitoto before the concert on Tuesday, Ziegler told her followers she was "a little bit obsessed" with New Zealand.
"I don't want to be critiqued about the way that I look on the Internet", she once said on Nightline. If that changes, we stop'.