During an appearance on ITV's Loose Women, Vardy broke down in tears as she said she was trolled by members of the public after Rooney alleged she had turned detective to prove Vardy's Instagram account was the source of leaked stories about her private life.
Vardy - who denies any wrongdoing - said she could not say too much about her argument with Rooney while on the ITV programme because "we are in the middle of a legal battle".
But she did say: "It was really, really hard, it's probably up there with one of the worst things I've had to deal with, apart from being abused by my stepdad when I was younger."
Vardy, 37, said she learned Rooney had gone public with her suspicions on social media while she was on holiday in Dubai with her husband, adding that the trip "didn't end up too well".
She added: "It was hideous, it was horrible and I don't think I was prepared for what was to come.
"It just escalated, really... the trolling was the worst part for me and my family. I've been trolled before but this escalated off the back of it, it was a whole new level."
She cried as she read out a message from a troll.
She said: "I had people messaging me saying nasty stuff, one in particular said, 'You fat ugly rat, I genuinely hope you and your baby rot."
Vardy added: "I had severe anxiety attacks. I ended up in hospital three times, and I ended up with kidney stones.
"I felt like I couldn't go out, I had people just looking at me just questioning, 'did she do it? Did she not do it?'"
She said Jamie "really struggled seeing me upset", and her 15-year-old daughter Megan also faced negative messages on social media.
Vardy added: "It was a hard time."
Focus on baby daughter
Vardy welcomed baby daughter Olivia Grace on December 28, and she said she is trying to focus on looking after her.
She said: "It's a new year isn't it, it's 2020 and it's time to focus on some exciting things that are happening, the family and the new baby, and babies need healthy mums."
Rooney, 33, sparked the #WagathaChristie trend on social media in October for her sleuthing work after she said she had spent five months attempting to work out who was sharing information about her and her family based on information she had posted on her personal social media page.
Rooney, the wife of footballer Wayne, claimed she worked out it was down to I'm A Celebrity... Get Me Out Of Here! star Vardy's Instagram account following a process of elimination.
She blocked access to her private Instagram account to everyone except Vardy's page and planted a series of false stories that later found their way into print.
At the time, Vardy said third parties had access to her Instagram account and an expert was working to discover who could have been behind the leaks.
She also revealed she had phoned Rooney for a conversation.
Vardy told the Daily Mail in October: "I thought she was my friend but she completely annihilated me. She said: 'You know, I always really liked you, which makes it harder.'"