The presenter and DJ, who is now married to Made in Chelsea star, Spencer Matthews made the comments on the pair's new podcast 'Spencer & Vogue'.
Williams was married to the former Westlife singer for three years, with their wedding being held in Florence, Italy in 2012.
In 2015, the couple announced their separation.
Speaking on the podcast, Matthews brought up the topic of her former marriage certificates, complaining that he had to see them every time he goes into their safe.
Matthews said: "Every time I go into the safe, by the way, I have to see your marriage certificates because like we needed them for a mortgage and I just have to look at them."
Williams added that she was glad she did not have to look in the safe, saying "it makes me feel a little bit sick in my mouth".
"Sometimes I forget it ever happened," she said.
McFadden has not yet commented on his ex-wife's remarks.
