Kristina, 38, is currently in a relationship with rugby hunk Ben Cohen, a romance she’s consistently been forced to defend following his marriage breakdown last year.
But before 36-year-old Ben, professional dancer Kristina enjoyed a brief fling with Vincent, also 36, and she insists she had no idea he was in a relationship.
In extracts from her upcoming autobiography Dancing Out of Darkness: My Story, published by The Sun, she said: “[Vincent] was very charming and he was paying me a lot of attention.
“In my defence, he acted like a single guy and totally dismissed that he had anyone in his life. He never said he had a girlfriend. He said there was a girl who was very much in love with him and that it was complicated.”
But Kristina had no idea just how complicated Vincent’s situation was – and the revelation brought her world crashing down.
She continued: “He asked me to come into his room. I thought we were going to talk about what would happen with the relationship now the tour was ending.
“He simply said, ‘The girl that I told you about, she is my girlfriend and I can’t leave her now because she is pregnant.”
To make matters worse, Vincent also revealed his girlfriend was four-months gone. Kristina added: “I felt absolutely sick to my stomach. My legs almost gave way, they were shaking so much.”
After Vincent, Kristina enjoyed a four-year romance with another Strictly co-star – boxer Joe Calzaghe, who she was patented with for the 2009 series of the BBC One show.