The 18-year-old, who failed to get past bootcamp on last year's show, will be seen performing to Prince's Purple Rain.
Speaking backstage with her nan - who Chelsea calls her inspiration - the teenager admits: "I’m scared of getting buzzed."
On stage, Chelsea admits to the judges: "At the moment the I do admin office work for my dad but I’d really like to be a worldwide singer."
Bursting into a performance of Purple Rain by Prince, will the X Factor judges regret their mistake?
Other acts on tonight's show include dance troupe Twisted Disco, who reckon they put a unique spin on typical dance acts seen on the show.
But an unimpressed Simon Cowell remarks: "It was like 18 Jodie Marshs on a night out."
Britain's Got Talent 2012 airs at 8PM on ITV1 tonight.