"Yeah, I was surprised," the former Suburgatory star, 48, told PEOPLE at the Groundlings 40th Anniversary Gala in Hollywood on Monday night. "It's very sweet. There are a lot of people that are excited about it."
Not least, Hines herself.
"It feels great because you know you're going to be with the person you really like to be with for a very long time. And that's a great feeling," she says of Kennedy, 60, whom she has dated since 2012.
Hines wouldn't reveal just how Kennedy proposed but did confirm that wedding preparations are already under way – when they get a spare moment, that is.
"The details have not been ironed out," she said. "We're trying to get all the kids graduated from school, on to college, that sort of thing. We're getting ready for summer. Lots of sailing and swimming and lots of activities. Everyone moves together as a group. It's a little bit of chaos at times. But it's great."
And one question on everyone's mind: How does it feel to become a Kennedy?
"I come from a big family, and the Kennedys are a big family. It feels natural," Hines said. "When I met them, they were all very genuine and gracious. I was surprised. I didn't know what to expect or who they are. They're the most generous people I've ever met."