It was a Bachelor party at the Thompson Beverly Hills hotel rooftop on Saturday.
At the pool party, Fedotowsky – who showed up sans new beau Kevin Manno – “grabbed Sean and Catherine and congratulated them on everything,” an onlooker tells PEOPLE. “Sean spoke about his recent stint on Dancing with the Stars and he and Catherine joked about them having choreographed a wedding dance.”
Adds the observer at the Joico and Olay-sponsored event: “The couple seemed happy and definitely in love. Catherine mentioned that she wants a very mellow and intimate bachelorette party.”