"Everybody deals with something like that," the Chicago star told PEOPLE at an event to launch Hershey's new Pieces candy line in New York's Times Square Wednesday. "The thing about growing up is that you grow into your own and find the things that you think are beautiful about yourself."
Simpson-Wentz, 25, believes her sister's upcoming VH1 reality show The Price of Beauty, which explores what beauty means in different cultures, will make the curvy blonde even more relatable to fans. "This is something all women can relate to – that's what's so great about her show," she says.
As a new Hershey's ambassador, the singer admitted she must keep an eye on her own sweet tooth. "I'm definitely a candy person [and] Reese's is my favorite," she said. "But I have to make sure to do everything in moderation."
One thing Simpson-Wentz doesn't hold back on? Doting on son Bronx, 14 months. "He's such a boy," she says. "Right now, he's really into reading books and building forts." He's also into spending time with his Broadway-star mama. "Bronx comes to the theater on the weekends to visit," she says, "so we get to have lunch or dinner there together pretty often."
And while they do spend a good deal of time apart – Simpson-Wentz hits the stage for eight performances each week – she knows her little guy is out there, supporting her. "He came to a rehearsal, and yelled out 'Mama!' when I got on stage," she says. "It was really cute."
Reporting by Sabrina Ford