Next stop was Smashbox Studios, Los Angeles's premier photo studio, where her music video was already under production.
After a quick introduction by Wilson to the "wizards," the crew behind her video, St.George got to work, matching the dance moves she mastered with Taylor to the vocals and lyrics she perfected with Wilson.
"Off camera, she's serious," Wilson said of his performer. "But I say action, and she has a smiley face."
"She never gets tired," he added. "Literally, in the one day we shot 80 percent of the video."
But will focus, endurance and that "star factor" be enough to make the California teen America's next pop star?
"Watch "One Week to Hit It Big" on "Good Morning America" all week to follow winner Lexi St.George inside the making of her song, and then the premiere of her music video Thursday.