The TV judge got a taste of what the contestants go through when she took to the stage on December 2 to sing her new single Sight Of You.
"That was terrifying, I don't even want to talk about that - I've never been so scared in my entire life," she said on This Morning.
"For some reason just doing it there - the pressure is completely different. I just felt like I was being judged so much that it literally cracked me... It was more to do with the overall pressure that I had - I let it get to me."
The 24-year-old, who performed at the top of the BT Tower as part of the BT Infinity Presents... Live from the 34th Floor last night, revealed recording her debut solo album The Female Boss, without her N-Dubz bandmates Dappy and Fazer, was a daunting experience.
"The whole process is scary. And being so used to having the boys with me either side, and what direction I was going to take it in as well, but luckily it just kind of came natural when I was in the studio," she said.
"We've had loads of talks. I think we just all need to sit down as a three and have a little meeting and go, 'If we're going to do it, then let's put a date on it'," she added.