The 12-year-old gave a stand out rendition of 'Someone Like You' from the musical 'Jekyll And Hyde' as she competed in the fourth live semi final on Wednesday (25 May) night.
Beau was branded a "potential winner", as Simon Cowell claimed we'd witnessed the birth of a star.
Amanda remarked: "I’m so proud of you. That's a beautiful song. Your voice, I think, was even better than your actual audition, which I didn’t think you’d be able to do. I could not be more thrilled for you."
Simon added: "When I was sitting there watching you, it wasn’t the fact you’re 12-year-old with a good voice, you’ve just got an incredible voice. You choice of songs is impeccable, your performance skills are sensational.
"I guarantee you in about five or ten years time, we’re all going to look back to this period when we first saw you and say, ‘This is the moment we discovered a star.’ I can feel it."
Beau's original audition, where she sang ‘Defying Gravity’ from the musical ‘Wicked’, was so impressive that Amanda hit her Golden Buzzer, granting her an automatic place in this week's semi finals.
However, Beau was later at the centre of controversy when it was revealed she'd had experience on rival talent competition, 'Teen Star', and also had formal singing training.
A 'BGT' spokesperson spoke out to defend the young singer, who said she still suffers from nerves, stating: “Just because she has had singing lessons, it doesn’t mean that she doesn’t get nervous when performing as was stated on the show.
“Adele, who is the biggest selling artist in the world, suffers from nerves when performing, so it’s not surprising to think that Beau would as well, especially given that she is a 12 year old schoolgirl.”
'Britain's Got Talent' continues tomorrow night at 7.30pm and 9.30pm on ITV.