Last week, Williams, 54, filed for divorce from Hunter, ending more than two decades of marriage. And the source says she left Hunter after he admitted he had been unfaithful.
“The split is definitely due to Kevin’s ongoing infidelity and that his mistress recently welcomed their child,” the source says. “Wendy had hired a private investigator and confronted him. He confessed to everything three weeks ago.”
PEOPLE was unable to reach Hunter and his alleged mistress for comment. A rep for Williams could not be reached for comment.
“All of the recent drama put a huge strain on Wendy and caused her to struggle with her sobriety as she did everything she could to try and save their marriage,” the source says.
Filing for divorce wasn’t an easy choice, either.
“The decision to split was terribly hard for her, but she’s regaining her health. She decided she needed to finally put herself first,” the source says.
On Thursday, a source confirmed to PEOPLE that Williams had filed for divorce from Hunter. The pair wed on on Nov. 30, 1997, and share son Kevin Jr., 19.
“Thank you to everyone for respecting the family’s privacy during this time. Kevin is supportive of Wendy and they are working through this process together,” the personal representative for Williams told PEOPLE in a statement at the time. “No additional comment will be provided at this time.”
A representative for her show released the following statement: “Wendy and her family have been a part of Debmar-Mercury for over 10 years,. We respect their privacy regarding personal matters. As always, we remain committed to bringing an entertaining and topical show to our viewers.”
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Days later, during Monday’s episode of The Wendy Williams Show, Williams alluded to the drama while reflecting on the motto of her Hot Topics segment, “Their business is our business.”
“It’s crazy ’cause now my business is your business,” Williams said with a laugh. “It’s kind of funny. Turnabout’s a fair game, I get it.”
Williams, who recently revealed that she had been living in a sober house, said she had a “really good weekend” and got together with six of her friends from the facility. (Two of them are her sponsors.)
“I’m moving out of the sober house in just a few days, you know,” she said. “It’ll be Wendy on her own.”
“I have to tell you, you know, I’ve been dealing with issues with addiction, alcoholism, and I have a whole new life that I planned for myself and my son,” she continued. “Believe me you, when you lay in a room with no TV and four gray walls all day … this is my life in the sober house, it’s one of the best things, honestly, that could have ever happened to me.”
PEOPLE’s source confirms, “She’s ready to leave the sober living house and build a new life for her and her son.”
Williams, who has long been open about her past addiction to cocaine, said speaking candidly about her struggles on her show has helped her recovery.
“You wear a different mask when you’re out here,” she said. “Everybody has things in their life that they’re … not ready to share with the world.”
“Addressing my sobriety, my addiction, head-on has really helped me sort out every single compartment of my life,” she said. “I have a commitment to me and my son to come out of here better, stronger and faster than ever. And by the way, I will still commit. … I commit that the motto of this show will always be, ‘Their business is our business.’”
Hunter’s alleged affair isn’t his first: He cheated on Williams after she gave birth to their son, a painful period she described in her memoir Wendy’s Got the Heat.
Still, she stood by her man for years.
“It has made our marriage — and I know this is cliché, but it’s true — it’s made our marriage stronger,” she told VladTV in 2013.
“No, I’m not back to the girl I was before him, because when you get stung like that, you never go back to who you were — only a fool does,” she continued. “But I love him, and he loves me, and we addressed it head-on.”