The East London-born singer claimed second place in eleventh series, losing out to fellow contestant Ben Haenow on tonight's grand finale held at SSE Wembley Arena.
Fleur told Sarah-Jane Crawford on Xtra Factor: "I just feel so grateful! I think when I stood on stage tonight, it was the first time I realised what has been happening these last three months.
"I couldn't be happier. And I love Ben. I'm so happy for him."
She added to the audience: "I want to say thank you so much because you have brought me the closest I've ever been to realising my dreams, so thank you."
"This has been the most stressful, intense, emotional experience of my life and I can't believe I am here!" she continued. "I always put in my mind if I can get to every stage of the competition I'll be happy and I did that and I'm so happy. And I'm so happy for Ben."
Fleur had gone into this weekend's finale as the bookies' favourite, following incredible performances such as 'Uptown Funk', which she chose as her song of the series.
She had been mentored by Simon Cowell across the series.
"Thank you for believing in me," she told Simon. "Thank you for trusting in me and giving me the chance to do this."
Simon replied: "She just turned into a completely different artist in the last few weeks. She's been a pleasure to work with."
Music mogul Simon also mentored winner Ben Haenow and said on Xtra Factor he believed both Ben and Fleur would go on to have careers in the music industry.
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