The 12-year-old's confident rendition of the Soulja Boy hit provokes a standing ovation from the crowd and a positively emphatic response from the panel.
Simon Cowell beams: "I like it when kids your age choose the song, rather than your mum and dad choosing it for you."
Cowell also displays amusement at the fact "the guitar was too big" for the schoolgirl, adding: "Because you're posh and you're talking about swag, it's even better."
Even upbeat about Thalia's musical faults, Cowell added: "You couldn't play it that well and there was a little break in your voice but actually it made it more believable."
Meanwhile, Alesha Dixon comments: "You're as cute as a button, you are adorable, well done."
David Walliams compares Thalia to "a very tiny" version of Grammy Award-winning singer Alanis Morissette.
Britain's Got Talent airs Saturday from 8.30pm on ITV1.
> 'Britain's Got Talent' auditions week five preview - Pictures
> Stephen Mulhern's 'Got Talent' blog week five
Watch a teaser clip of 12-year-old Lauren's performance below: