The Grey's Anatomy star tells PEOPLE she and her fiancé are planning an intimate affair

Ellen Pompeo’s upcoming wedding won’t be a lavish production – but her co-stars might need to make some travel plans if they want to attend, she says.

“There will be no ‘big’ anything,” the Grey’s Anatomy star, 37, told PEOPLE Saturday at the Chrysalis Butterfly Ball, a benefit for the homeless in Brentwood, Calif. “It’s going to be very small.”

Beyond that, she and record producer Chris Ivery, who got engaged in November, are keeping mum on the details, but Pompeo hinted that the ceremony won’t take place in Los Angeles: “We were thinking about going away and getting married.”

The actress was reunited Saturday night with some of her co-stars for the first time since production on Grey’s wrapped several weeks ago. Also at the gala, hosted by Eric “Dr. McSteamy” Dane’s wife Rebecca Gayheart: Patrick Dempsey, Kate Walsh, T.R. Knight, Justin Chambers, Sara Ramirez and James Pickens, Jr.

Pompeo said that when Ivery proposed on her 37th birthday, she was only slightly caught off guard. “Chris and I have been together for four and a half years, so I was completely surprised, but not that surprised. We’ve been together a while.”

Ivery – like her, a Boston-area native – has changed her life because “I just have somebody to share everything with,” she said, “all of these moments. The bad ones and the good ones. We have a very strong bond, and we just understand each other. He’s just a real companion.”

She added that she knew Ivery was “the one” early on: “I guess you fall in love and you think he’s the guy right away. Right when you fall in love, you think he’s the guy. You don’t sort of fall into a relationship thinking it’s only going to be temporary.”

The couple met in a Los Angeles grocery store in 2003 and began dating about six months later after “one night she just looked different to me,” Ivery, 38, told PEOPLE late last year. They quickly discovered that they had grown up about 10 miles away from each other in Massachusetts and that Ivery had met Pompeo’s father there.

“We have a lot in common,” Pompeo said Saturday. “We’re from the same hometown, almost.”

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