The N-Dubz star is rumoured to be dating bandmate Fazer, given that the pair were "sleeping together on and off since they were in their teens".
However, she remained coy about the romance after giving an interview to The Sunday Mirror in which she discussed her relationship.
"What I will say is I'm really happy and have the best boyfriend - he's very supportive in what I'm doing with the show," she told the paper. "He's my rock - he's been there for me throughout the past few months. I couldn't be doing what I'm doing without him."
The X Factor judge later wrote on Twitter: "What r all these tweets about Fazer, I've spoke about my relationship, I neva said it was with him? Hmmm (sic).
"Just as I suspected, I have never said I was in relationship with fazer, only said what my boyfriend meant 2 me, did not say who he was."
Contostavlos recently confessed that she feels her X Factor job still belongs to Cheryl Cole.
Watch Contostavlos and Fazer in N-Dubz's video for 'Morning Star' below: