Grace VanderWaal on her new album: 'I've been writing left and right!'

Carly Mallenbaum | USA TODAY

Grace VanderWaal is standing a little taller on the America's Got Talent stage, one year since winning the show's grand prize.

OK, a lot taller.

"I grew 5 inches!" she announces at the start of her dress rehearsal at the Dolby Theatre, where in under two hours she'll perform her song Moonlight to millions of TV fans, and mark her triumphant post-win return to the NBC stage.

Seriously, she's 5-foot-3 now. At least 5-5 in her shoes.

VanderWaal, who signed to Columbia Records and Simon Cowell's personal label Syco Music since being crowned champion, has also grown professionally in the last twelve months. She released a successful EP in December, won a Teen Choice Award, just announced several tour dates (she'll be playing three cities in November and several more in February), learned to embrace performing ("It's my favorite part" of being a musician.) and has spent the past few months working with producers ("I've been writing left and right!") on an album out this November.

Still, there's nothing that can make her feel comfortable back on the AGT stage. Not even her adorable pug Frankie, who VanderWaal tows everywhere, can stop VanderWall from yelling, "I'm so nervous!" ahead of her performance.

Returning to the show, "it’s just like green air of anxiety just filling out my lungs," she says.

That explains why she's being so meticulous about her act.

"Do I look like a silhouette?" she keeps asking, as the tech team repositions her microphone, fans a fog machine and adjusts onstage trees to help achieve her desired "dramatic opening" look, as she calls it. When VanderWaal is finally assured that she does, indeed, resemble a dancing human shadow, she seems to remember that she's only 13. The young singer makes a Taylor Swift-esque mic-in-the-air move, flexes, then does a three-finger Hunger Games salute and whistles the theme from the movie.

She's just a kid. Until she isn't at all.

"I feel like the elder," VanderWaal says backstage, comparing herself to AGT's Season 12 contestants. "Oh, little babies, they'll grow up soon," she jokes. "I wanna tell them, ‘I’ve been through this. I know exactly what you’re going through right now. You can do this. It gets easier.'"

Her maturity indeed shows when she tells a photographer that a suggested pouty pose "isn't me," when she gives a makeup artist specific instructions to make "little shimmers on the tip of my nose and a little cupid's bow," and when she confidently tells her manager that blue and purple-colored lights would look best onstage.

However, though she acts like a pro, VanderWaal doesn't always feel that she's taken seriously. That's what Sick of Being Told, the first single off her as-yet-untitled album, is about.

"I remember I had a writing session that day with a producer, One Love (Pitbull, Beba Rexha), and I was kind of going on a rant (about how my team passed on an idea for the Moonlight video)," she says. "I was like, ‘I’m so sick of it.’ I’ve done all these things, and so many people have told me, ‘No, you’ll fail. You’ll end your career. You’ll get voted off.’ And I do it and it works great."

She's not wrong: Already her Los Angeles and Atlanta shows have sold out, her Perfectly Imperfect EP debuted in the top 10 of the Billboard charts and her new YouTube videos — including the one of her AGT return performance — continue to garner hundreds of thousands of views.

But sometimes even an artist with a strong sense of self just needs her daddy.

After VanderWaal tapes her performance for the show and fulfills AGT-related social media obligations, she's wiped. She finds her father, Dave VanderWaal, whose sparkly red nails are the same as his daughter's (she painted his nails for today's "special occasion," he says). He holds Grace's hand, and then scoops her up in a piggyback ride.

"I just wanna lay down (and) watch the rest of the show from bed," she tells him.