The "Chandelier" hitmaker admits she is "fiercely protective" of the young dancer and actress as she knows how demanding it can be to live her life in the spotlight.
Discussing her own learning curve on dealing with fame, she told Sirius XM's "Fierce: Women in Music", "I had to just learn really, really good boundaries. And now I'm really good at it and if somebody wants to say hello, I'm totally comfortable with that. If they want to take a photo it depends on what the situation is, but I'm either totally comfortable doing that or I'll say, 'Actually, I don't want anyone to know that we're here...' "
She added of taking care of Maddie, "I provide her 24-hour security because I feel responsible for her ensuing fame."
And whenever Sia is with Maddie, she can often tell if the 18-year-old is in the mood to interact with fans or not.
"I can tell from Maddie's face whether she wants to do it or she doesn't," Sia shared. "And so I either say, 'No, you know, we're not supposed to be in town' or, 'We're not doing photos today' or, 'Actually we're just having some family time.' "
Sia and Maddie collaborated on numerous projects. The latest one is a new movie "Music" where the "Dance Moms" alum plays an autistic girl who moves in with her newly-sober half-sibling Zu, portrayed by Kate Hudson.