Regarding her time spent with Katy Perry, Sia felt she never quite jelled with the "Fireworks" singer, whom she describes as "quite dominant, and she's extremely analytical. I actually quit within the first hour of our first session." Perry convinced Sia to stay on
"I think that the stuff I write for pop music is terribly, terribly cheesy" she admits in the interview, though the reception of said cheese has helped her come to terms with the fact that a song can be both popular and meaningful at the same time.
She also takes about her experiences with Beyonce, Adele, Rihanna, and Kanye. I got the impression she very much liked the first two. But yeah, was surprised to hear this.