Courtney Hadwin finished in the top three on Monday as the British schoolgirl competed on America's Got Talent: The Champions.
The 14-year-old singer from Hesleden, in County Durham performed her own song Pretty Little Thing that saw her transform from a shy teenager into a wild rock star.
'That was bloody fantastic,' Simon Cowell, 59, told Courtney while admiring her newfound confidence that saw her blowing kisses and high-fiving the judges.
'I think this has been my favorite performance by you so far,' he insisted.
Heidi Klum, 45, said she turns 'into this lioness and you roar it out' onstage, adding: 'You're just so cool.'
'You are a champion, hands down you are,' Mel B, 43, told her.
Courtney was a finalist last year on season 13 of America's Got Talent and finished in sixth place.
She reached the final three on Monday and finished in third place as 10 international acts performed during the two-hour episode.
AGT season 12 champion Darci Lynne Farmer, 14, finished in second place and Got Talent España winner Cristina Ramos took first place and landed a spot in the finals.
Cristina started Bohemian Rhapsody with ethereal opera – then switched to hard rock after a firecracker flash, with Heidi saying she went from 'Maria Calas to Courtney Love.'
'That was brilliant!' Mel B screamed. 'I mean this is what I love about this show. Just when you think there's this beautiful innocent girl singing such love melody opera – boom! Out comes a firecracker! Boom boom boom!
'I loved it. You're a very beautiful woman.'
Howie Mandel, 63, said they 'always looked to be surprised,' adding: 'I think people are going to be talking about you tomorrow. I believe everybody didn't expect that.'
'I mean it was spectacular,' Simon agreed. 'Your voice is off the charts. This was unbelievable – I mean really, really unbelievable.'
Even that high-praise did not seem to prepare her for the shock of getting through thanks to the votes of super fans from all 50 states.
Afterward Cristina said she was 'speechless,' as Simon assured her: 'You got there on talent.'
Deadly Games earlier advanced to the finals after receiving Heidi's Golden Buzzer pick.
Their terrifying act culminated in a high-powered crossbow being fired at a handkerchief held by Anna – with only Heidi Klum's cellphone camera to direct Alfredo who had his back turned on the target.
The daring duo already were shaken by an accident in rehearsals of season 12 of AGT.
The reality of dangerous acts then hit too close to home when Alfredo's sister fell 30-foot onto her head during her act as an aerialist, leaving her wheelchair-bound.
'I wanted to give up,' Alfredo said, admitting he feared for wife Anna, the mother of his child, saying: 'What if I hurt her – kill her – it could happen.'
The episode's first performer was Darci Lynne, the singing ventriloquist who won AGT season 12.
'You are the epitome of a dream coming true,' Howie told her after her act where she teased Simon for always wearing the same clothes and sang rock classics Nutbush City Limits and Proud Mary.
'I was literally blown away by that,' Simon told her. 'Apart from being so charming and funny, you've actually got this incredible singing voice. But you've got this killer competitive instinct as well. And that's what makes you a star.
'I think you deserve to be the world champion.'
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