Allison Kaye

When your client -- in this case, Justin Bieber -- releases a critically acclaimed record that debuts at No. 1 on the Billboard 200, earns 1.6 million equivalent album units in the United States and generates 1.7 billion on-demand audio streams, there is no such thing as sitting out the accompanying tour, even if you're seven months pregnant. "It's not the first time I've toured while pregnant, but it will be the last," says Kaye, one of the principal architects behind Bieber's Purpose World Tour, which has grossed more than $139 million so far.

Underscoring the mother of two's resilience is her feat in helping execute one of the most successful image makeovers in recent pop history, transforming the Biebs from a house-egging public urinator into a matured, sympathetic heartthrob. "We took Justin from being maybe the most hated person in the music industry two years ago, to people seeing he's just a good kid who was going through it," says Kaye, whose own tight-knit relationship with the wunderkind has metamorphosed since they met in 2009.

Promoted from GM in July, Kaye will now focus more on "putting out fires" and remaining hands-on with clients Ariana Grande, Kanye West and Tori Kelly. But balancing the demands of her job with family life? "Sometimes you have to realize you can't be all things to all people, and that's OK."