"#letscelebrate," Cook captioned a photo of the couple embracing via her Instagram Story Thursday night. "Today I said YES to the man of my dreams. You complete me!" she added in another, which showed David, 54, shirtless and kissing the head of his new fiancée.
She went on to post a smiling selfie with David on her actual feed, showing off her massive new bling. "Looking forward to eternity with my love, I LOVE YOU LOVE!!!" she captioned the image.
David and Lesley began dating in 2017 after meeting at a SoulCycle class, very shortly after David and Shannon, 55, called it quits on their 17-year marriage. Shannon said she learned that her estranged husband had moved on via Instagram.
"David and I communicate through text and email, and they aren't pleasant," she said during the "RHOC" Season 13 premiere. "I found out two days after it was all over social media that David has a new girlfriend that is almost 20 years younger than him."
"It's understandable that at some point he's going to move on, but to know that I'm so easily replaceable within a couple months, it hurt and I cried a lot," she later said to Vicki Gunvalson. "She's one of 3,000 young girls that want some guy to take care of her."
Tamra Judge then suggested that David -- who admitted during Season 10 that he had had an affair during his marriage to Shannon -- had been unfaithful to her with his new girlfriend, too.
"He was commenting on her posts in October," Tamra told her friend, adding in a later confessional, "After I found out that David had a girlfriend, of course I started stalking [Lesley]. And I saw that they had been communicating as far back as maybe even when [David and Shannon] were married."
"It doesn't matter. It's over. It doesn't matter," said Shannon through tears. "I wouldn't put it past him." That season, Shannon struggled to take off her wedding ring and accept her new life as a single mother. Bravo cameras captured several emotional meltdowns stemming from the stresses of her divorce, including self-loathing over her weight gain.
During Season 14, however, Shannon came into her own. She lost 40 lbs and revealed to TooFab she had a new boyfriend by the name of John Janssen.
"I kind of made a commitment to myself that I wasn't gonna get involved with anyone because I know that with my age..." the reality star told us. "I want to eventually have a partner, but I'm older. I kind of have one shot left, so I wasn't gonna just jump into a relationship. That being said, I did meet John, and it was a surprise, and I had a connection and a comfort with him that I haven't experienced with anyone before, so I'm really grateful that he's in my life."
At the time, Shannon told us it was a "new relationship" and that the two had been dating for "a couple months." They met through "mutual friends" despite the fact that they "both went to USC." Because he was a couple years older than her, they never crossed paths on campus. Shannon said her daughters -- Sophie, 18, and twins Stella and Adeline, 15 -- had met John and that they liked him "a lot."
"They see that I'm happy, and they want me to be happy," she explained. The two are still together.
Shannon and David announced their separation in October 2017, and she filed for divorce two months later in December. The former couple's contentious divorce included a nasty custody battle over their daughters and disagreements over money. The divorce was finalized in April 2019.