Rooney, 34, posted that she had sought the culprit for the leaks by blocking everyone apart from an Instagram page belonging to Vardy from seeing her Instagram stories, and then posting "a series of false stories to see if they made their way into The Sun".
Both women are celebrities in their own right, and married to famous footballers - Rooney to former Manchester United and England star Wayne Rooney, Vardy to Leicester City and England striker Jamie Vardy.
As regards the process in question, Mrs Rooney claimed she had blocked everyone except one user from viewing the fabricated "leaks".
Lawyer Hugh Tomlinson, acting for Vardy, said his client was depicted as a "villain" in an "untrue and unjustified defamatory attack. published and republished to millions of people".
"I have saved and screenshotted all the original stories which clearly show just one person has viewed them", Rooney posted.
Prior to her sighting, it was revealed that Coleen is feeling confident of winning the libel case against Rebekah but regrets that it has got "this far", after she infamously accused Rebekah of leaking stories about her to the press.
She was pregnant and on holiday at the time of the accusations, and described herself as "so upset" by the claims.
At the hearing, Mr Justice Warby was asked to determine the "natural and ordinary" meaning of Mrs Rooney's posts.
A source said: 'Becky is set to swear publicly and on oath to the High Court that she was not the so-called Secret Wag for the newspaper'.
The barrister also said the parties had agreed for a "stay" of the proceedings until February, so there could be "one final attempt to resolve the matter without the need for a full trial".
David Sherborne, representing Mrs Rooney, said in written submissions: "It is true that the claimant was responsible for consistently passing on information about the defendant's private Instagram posts and stories to The Sun, and that this was part of her history and practice of providing private information to the press, especially The Sun, with whom she had a very close relationship".
But for her part, Rebekah is seeking substantial damages and says she has suffered "severe and extreme hostility and abuse" in the fallout after the claims were published on Instagram.
The judge said he would issue a ruling on Friday.
Neither Vardy nor Rooney was in court for Thursday's preliminary hearing.