The 42-year-old actress and husband Benji Madden joined Richie and her spouse, Joel Madden, for dinner at Il Ristorante Di Giorgio Baldi in Santa Monica, Calif. Both couples dressed in all black with the exception of Richie, who added an orange coat over her dark ensemble.
"Cameron is a regular and looked bella," a source told People magazine. "She seemed excited to be celebrating her first Valentine's Day with Benji. She and Benji looked very happy. They had a fun, three-hour dinner with Nicole and her husband."
"Cameron was having a great time," an eyewitness added to Us Weekly. "She was full of energy and was a chatterbox the entire meal. She was whispering to Nicole and laughing, and then looking over at Benji and Joel and laughing. The four of them seemed to be super close."
Richie and Joel Madden wed in December 2010, and have two children, daughter Harlow and son Sparrow. The 33-year-old designer introduced Diaz to Madden's twin brother and bandmate, Benji Madden, and the couple married in January after several months of dating.