In an October 2019 Twitter post, Mrs Rooney, 35, accused Mrs Vardy, 39, of leaking stories about her private life after a months-long “sting operation”.
The wife of former England star Wayne Rooney dubbed “Wagatha Christie”, claimed Mrs Vardy had shared fake stories she posted on her personal Instagram account with The Sun newspaper.
Mrs Vardy, who is married to Leicester City striker Jamie, denies the accusations and is suing Mrs Rooney for libel.
Mrs Rooney’s lawyers previously claimed that Mrs Vardy had leaked information to The Sun either directly or through her agent Caroline Watt “acting on her instruction or with her knowing approval”.
Mrs Rooney is bringing a claim against Ms Watt for misuse of private information and during a hearing on Tuesday and Wednesday, asked for it to be joined to the libel claim.
Her barrister David Sherborne told the court that, if Mrs Vardy wins her claim on the basis that she was not the person who leaked the information, then Mrs Rooney will be left without “vindication” unless she is able to bring the claim against Ms Watt as part of the same case.
Mrs Vardy’s lawyers opposed the application to add the claim against Ms Watt to the libel case.
“If the defendant had genuinely wished to bring a misuse of private information claim against Ms Watt in order to vindicate her rights this claim could have been brought 15 months ago,” Hugh Tomlinson QC, for Mrs Vardy, said in written arguments.
During the in-person hearing at the Royal Courts of Justice, lawyers for both women also applied for further information to be disclosed.
Mrs Justice Steyn is expected to give her judgment on the applications on Monday afternoon.