Coleen Rooney said a message between Rebekah Vardy and her agent about her dead sister “knocked her sick” when it was disclosed.
The 36-year-old took to the stand for the first time on the fourth day of the libel trial between herself and Mrs Vardy.
Mrs Vardy denies leaking stories to the media and is suing her fellow footballer’s wife for libel, while Mrs Rooney is defending the claim on the basis her ‘Wagatha Christie’ post was “substantially true”.
In a witness statement Mrs Rooney wrote: “While they were discussing her messaging me in order to cover her tracks, Becky says to Caroline Watt ‘maybe I should say something about Rosie’.
“Rosie is a reference to my sister who suffered with Rett Syndrome and passed away in 2013 at the age of just 14.
“The mere fact that Becky would suggest seeking to use Rosie’s name in conversation with me in order to put me off the scent of suspecting Becky as the person responsible for leaking my private information to The Sun is really low and sad.
“It actually knocked me sick when I read that message from Becky to Caroline.”
Earlier, Mrs Rooney told the court she named Mrs Vardy’s account as the suspected source of leaks to the press as a “last resort”.
At the heart of the case is a 2019 social media post by Ms Rooney which claimed information from private Instagram posts was getting leaked to The Sun through that account.
Ms Rooney said: “I wasn’t trying to achieve anything. What I wanted was to stop the person who was leaking my private information.”
The wife of former England captain Wayne Rooney told the court she had given out warnings “many times”.
But she added: “It didn’t stop and this was my last resort.”
Ms Rooney also told the court she was “surprised” by how much interest her so-called Wagatha Christie post generated.
She said she was “upset” her “personal information was getting passed on to a newspaper”.
“This was different. It was group of people that I had accepted into my personal space,” Ms Rooney said, referring to her private Instagram followers.
“I was making an accusation against her account,” she told the court.
“And I know that you have to give people permission to be on that account... I thought that Rebekah would know... and they she had given consent [for someone] to be on her account.”
Ms Rooney also told the court Ms Vardy, who is married to Leicester City striker Jamie Vardy, was “not in my circle” and she felt the 40-year-old would get in contact “to try and get information out of me”.
She said Mrs Vardy’s messages were “generally nice” but “towards the end its was a bit unusual”.
“Someone who was not that close to me... constantly checking in with me all the time,” Ms Rooney said.
Ms Rooney took the the stand after Ms Vardy finished giving her evidence - which spanned over four days - on Friday morning.
Ms Vardy ended by making a series of denials over the allegations that she was linked to leaks from Ms Rooney’s private Instagram account.
The 40-year-old model denied personally leaking information to The Sun, denied speaking to or messaging any journalists about any of Mrs Rooney’s posts, denied asking her agent Caroline Watt to pass on information and denied deleting messages from her WhatsApp.
The trial at the High Court in London continues.
