Transcript for How dance prodigy Maddie Ziegler went from 'Dance Moms' to being friends with Sia
She is a professional actress, music video star, people's choice award winner -- and also a middle schooler. She sits down with ABC's Abbie boudre Boudreau. Okay. One, two -- Reporter: You might not recognize her without that signature pixie and nude leotard. But I'm with Maddie zoeggeler. ??? the dancer you can't take your eyes off of. In video "The greatest." ??? she burst onto the scene at just 11 years old, dancing her heart out in the chandelier music video. The video viewed more than 1.5 billion times. ??? since then she's starred in four other videos including "Cheap thrills." ??? I got you baby ??? When I'm older I want to look back and go, wow, I got to do so many cool things. Even now at 11 years old, I had like over 1 million views on video. Billion. Yeah. Reporter: She may only be 14 years old but today she's got a new memoir called "The Maddie diaries." Full of stories from life in the spotlight. Hello, everyone. Reporter: Maddie may be wise beyond her years. But insists she's just like other teen girls. Even though not many have nearly 9 million Instagram followers. I feel like a lot of girls that it's hard to relate to me because I've done so many cool opportunities. But really I'm just like everyone else. Reporter: Maddie's rise from Pittsburgh to Hollywood began when she was 8. These are my daughters Maddie and Mckenzie. Reporter: When she was cast in lifetime's "Dance moms." A surprise hit. I'm an adult. Act like one! Reporter: Viewers couldn't get enough of the contentious relationships between coach Abby Lee Miller, her young students -- Oh my god, what is mentally wrong with you? Reporter: And their mothers. Including Maddie's momma Lisa. Melissa, you're doing your kid an injustice. I guess her take was she's making you better and better and better? Yeah, and I feel like since I'm such a perfectionist, I want everything to be perfect. Reporter: After six seasons, Maddie and her sister Mckenzie finally left the show. When they told me they didn't want to be on the show anymore, I was happy. I said, no problem. My sister and I were like, that's it. They were finished. Did you ever have that moment where you thought, as a mother, "Dance moms," this is breaking my daughters' spirit? Yeah, my gosh, absolutely. All the time. I was stressed out as a 12-year-old. That's really weird to me. Now I have so much weight off my shoulders. Oh, I can just live my life, do something without worrying and thinking, oh, I'm going to get yelled at if why this. Now I can do whatever I want. I mean -- stuff my mom lets me do. Reporter: Maddie has "Dance moms" to thank for one of the most important relationships in her life with Sia. She was a huge fan of the show "Dance moms." She tweeted me, will you be in my music video? I'm just like, that's crazy. Just wanting to wish you a very happy book release day. Grat latin realize you're my very special friend. I love you so much. I just adore you. Tell bus that relationship. The first time I showed her "Chandelier," the dance, she cried. Ever since then, we were just like best friends. It's weird to think, because we have such a big age gap. But people -- You're 14, she's in her 40s. Yeah. So people are like, how does that work? But we're best friends. She gives me a lot of great lessons in life to make sure that I'm not overworking or just making sure that I'm having fun with everything that I'm doing, which I really appreciate. Reporter: But some have criticized Maddie's dancing in Sia's videos for being too risque. A then 12-year-old Maddie's performance in "Elastic hearts" with shia labeouf. ??? were you surprised so many people were so concerned and thought it was so controversial? I think sometimes people have nothing better to do than hit behind their computer, their phone, and say mean things about you. I mean, it was a really cool video. Were you concerned with the video with shia? Not at all. No, I think it's art. Just like a play. I loved it. Reporter: Part of the art for Sia is concealing her identity. The singer famously hides her face in public, wearing her infamous wig. A lot of the people ask me, have you ever seen her face before? I'm like, it's not like she walks around with a wig in front of her face every single second of the day. It's only when she's in public and stuff. She's like the most beautiful person. And I love her so much. Reporter: The social media darling is taking her own recognition and building an empire of her own. Hey, everyone. It's Maddie. And I'm -- Reporter: From her addictive YouTube tutorials to her upcoming movie debut in "The book of Henry." You're living the Hollywood dream. People say that, you're a celebrity, you're famous. I'm like, I'm really not. I always think of myself, I'm just a Normal kid. Reporter: Like most teenagers, Maddie faces insecurities of her own. I'm not as on myself anymore as I used to be. It's okay to get knocked down sometimes. Because it does make you want to work harder the next time around. And also I'm okay to have imperfections. I'm okay with it now. I'm okay that I have some flaws. ??? Reporter: When you watch any of the Sia videos, what you can't help but notice is just how much fun Maddie is having. Do some of the crazy pieces you do in some of the videos. Reporter: Despite dance still being what she loves the most, she says what may be most important is being a role model for her young fans. Do you realize how big of a role model you are? I didn't really realize that until like last year. And there were kids that came up to me and said that they started dancing because of me. There was a girl that said she was going through rough times but then she looked to me and it helped her get through the rough times. It's really cool to think that I'm like a positive light in people's lives. Reporter: For "Nightline," I'm Abbie Boudreau in Beverly hills. Next --
This transcript has been automatically generated and may not be 100% accurate.