Cameron Diaz was spotted at the Academy's Hollywood Costume luncheon last Wednesday with a sparkling ring on her ring finger. Guests were quick to speculate that the "Charlie's Angels" star might already be engaged to her boyfriend Benji Madden.

She sat next to Gwyneth Paltrow during the Los Angeles luncheon, where an eyewitness described her as "casually and constantly twirling her ponytail, showing off the ring and often playing with it."

Diaz and Madden were also spotted grabbing a bite with their friends at an Italian hot spot, Madeo, in Beverly Hills. A source informed PEOPLE, that the actress was also showing off her ring there. The source revealed, "They arrived together with Benji driving. Cameron showed off her new ring and was smiling. They enjoyed dinner for several hours."

Benji Madden actually spent some time with the Diaz family in Florida last July. Certainly, with the meet-the-parents situation out of the way, it looks like the couple is about to take their relationship to the next level.

Additionally, another tipster told PEOPLE that the 35-year-old Benji Madden has actually already moved in with Cameron Diaz. The source said, "Since she started dating Benji, Cameron has changed in a very positive way. She can't stop smiling and seems much happier."

"Benji has lived with Cameron for the past couple of months," the source added. "They act like they can't get enough of each other and spend a lot of time together. During the days, they often share a workout. At night, they often stay at home and cook."

Another source also revealed that the couple has actually been talking "about marriage." The source said, "For a girl who was happy being single, Cameron seems to have fallen in love. She is really happy. The relationship is deep and she wants people to know it."

Also, Benji Madden seems to be equally smitten with his rumored fiancé. He was actually asked about his relationship with Cameron Diaz last August, and he told PEOPLE, "I'm really happy right now."