According to PEOPLE, it was during Saturday's performance of her Countess and Friends cabaret show at the Borgata Hotel and Casino in New Jersey that de Lesseps announced Mortimer hadn't participated in filming for the upcoming season of the Bravo show since getting engaged to Scott Kluth on Nov. 24.
During a Q&A session with the audience, Lu reportedly joked that Tinsley's mom, Dale Mercer, was "probably jumping for joy" over the engagement, though she felt Dale was likely "more upset that Tinsley's not filming anymore now that she's marrying Scott than Tinsley is."
But Luann doesn't seem to be holding any grudges against her co-star. "I wish her all the best," she told the crowd. "She seems very happy, and I want her to be happy and get married. That's what she wants to do. She's very traditional. She wants to have a baby. It's time."
"I just hope there's not [an alcohol-fueled fight] and the whole thing doesn't implode," she added cryptically.
Reports began circulating that Mortimer had quit "RHONY" to move to Chicago with Kluth in early November. Though she attended BravoCon with her co-stars, PEOPLE reports she has not been seen filming with them since and even skipped out on the cast trip to Mexico. The publication claims her exit from the show is expected to play out when Season 12 premieres in 2020.
TooFab has contacted Mortimer and Bravo seeking comment, but a source told PEOPLE that she walked away from filming with five weeks left on her contract.
"Scott gave her an ultimatum: 'me or the show,' and she choose the show," the insider said. "He loves the limelight but hated the negative effect the show had on their relationship. And Tinsley, she's desperate to make the relationship work and was on the outs with the group as it was."
"It was much easier for her to walk away from the friendships she was never going to have to fight for the relationship she always wanted," the source added.
Tinsley joined the cast of "RHONY" for Season 9 in 2017. That year, she was introduced to Scott via former co-star Carole Radziwill. They've been long-distance dating (he lives in Chicago) on and off ever since.
Scott proposed last month on the steps of the Chicago Water Tower.