In 2013, Sia Furler declared she didn’t want to be famous.

A music industry veteran and survivor of alcoholism, addiction to painkillers and depression, she described fame as a monster that “questions everything there is to question. Even things I had never thought to question. Things I had never dreamed of feeling insecure about.”

This creature was bent on “criticising you for an hour straight once a day, every day, day after day”.

“Me and fame will never be married,” she said.

In an attempt to control fame somehow, Furler put on her – now famous – oversized wig and stepped out of the limelight.

Well, she sort of did. She still made music and toured. On stage she wore the wig. She didn’t appear in her music videos. On her album covers there was all wig, no Furler.

She was half there.

I went to see her at her concert on Saturday in Sydney, along with tens of thousands of others. I didn’t really care about setting eyes on her, I wanted to hear her sing live. And she was amazing.

There, in the rain, she stood in her big white dress on a little white box, wig and giant bow obscuring everything up from her red lips. Her voice was beautiful. It was a great live moment. But Furler and her voice were only part of the show. A kind of backdrop, an anchor.

The actual performance, the moving part – the part for the eyes – was helmed by Maddie Ziegler: a 15-year-old dance prodigy who has been Furler’s cypher since she broke up with fame.

The pair began working together after Furler spotted Maddie on the US show Dance Moms and invited her to star in one of her videos.

A creative partnership flourished. Furler as the sound, Maddie as the the fury and the face. Furler had found a mini-me, a visual extension of herself. A “perfect blank slate”, as one report put it, who has starred in six music videos, a handful of live TV performances and now a global tour. And Maddie had found a platform for her substantial talent.

Furler’s use of Maddie in the music video for Elastic Heart caused a bit of fuss in 2015. The singer was accused of sexualising the dancer, then aged 12. She apologised, saying Maddie and the older male actor she danced with, Shia LaBeouf, were meant to represent two warring parts of herself. “My intention was to create some emotional content, not to upset anybody,” she said.

A still from the video clip for Elastic Heart by Sia with Maddie Ziegler and actor Shia LaBeouf.

Two years later she is still using Maddie to create emotional content. The dancer is not being overtly sexualised but she is being employed in a different way. And I can’t help but wonder what the consequences might be.

Up on the stage in Sydney on Saturday, with Furler concealed and Maddie in the spotlight, it seemed that the superstar was deploying a child in a way that she herself refuses to be.

Where Furler was hidden, Maddie was exposed. Where Furler was still, Maddie was moving. Where the singer was in darkness, the child was in the spotlight. Where Furler’s face and body was carefully hidden from the eyes of a stadium full of strangers, Maddie’s face and body was offered up instead.

Maddie’s face and body are extraordinary. She is a phenomenal dancer. So expressive, so wild in her movement, so magnetic. There were other dancers, they were good. But Maddie, the little Sia, was the star.

And so much of her dancing is in her face. She moves her hands across it, pokes her fingers into her mouth, as the camera – beaming that face a hundred times bigger into the night – goes in for close-up after close-up. But Sia is cloaked and protected.

Obviously, Maddie is not afraid of fame. She has more than 10 million Instagram followers and more than 1.2 million on Twitter. She is busy and ambitious and works on various projects outside of her collaboration with Sia. She is, presumably, embracing the career she wants.

But that doesn’t rub out the fact that, in this case, the grown-up who has seen what fame can do and fears it has, perhaps unwittingly, handed it over to the child instead.

Furler is a musician who is loved and respected by multitudes, she is a consistent creative genius and she appears to be a kind and thoughtful person who has a high-functioning sense of humour. All this makes the Maddie conundrum more perplexing.

Furler herself might not be willing to marry fame but standing on the stage in front of us, she seemed to be officiating another marriage. Not to a “perfect blank slate” but to a minor who is yet to learn about, or tame, the monster.