This weekend will see the acts in the four categories battle it out for just six spots at judges' houses.
Fleur, who wowed at the Arena auditions with Chris Brown's Fine China, said: "I’m just going to try and not be complacent, the Room Audition gave me the push I needed.
"I’m going to make sure that I’m fully focused and that I pull out all the stops."
She added: "I’ve got to go into it thinking that Boot Camp is a war and I have to fight to get through."
Fleur had originally made it to the live finals on the show back in 2005 as part of girl group Additiv Ladies, but says this time is completely different.
"It’s the first time I’ve done something like this on my own," she told the official ITV X Factor website. "But it feels like a massive achievement to have got this far.
"Going for that Room Audition I was nervous but when Louis gave me a no it really knocked me back. I actually questioned if I was even going to go back. It took a lot for me to walk in there on my own."
Fleur added: "[It's] So so different. It’s on such a bigger scale now. The team is bigger, the show is bigger and I think that’s why I didn’t feel prepared enough – it’s completely different."
X Factor airs this Friday, Saturday and Sunday on ITV.
Browse pictures from The X Factor 2014 below...