Denise Richards at Bow Wow WOW Howlywood
08/24/2009 AT 02:00 PM EDT
How does Denise Richards
feel about sending daughter Sam, 5, to kindergarten this fall? Let's just say, "it's complicated."
"It's bittersweet," the actress and reality star told PEOPLE Saturday night at the Much Love Animal Rescue
's third annual summer fundraiser Bow Wow WOW Howlywood! in Los Angeles. "Sami starts kindergarten, which I cannot believe, in a couple of weeks. I'm so sad about it."
Richards, 38, who has two daughters with ex-husband Charlie Sheen – they're also parents to Lola Rose, 4 – said the time has flown by. "I can't believe how fast five years have gone," she says. "I'm very proud of her and very happy, but from here on out she's in school."
Richards, who has rescue dogs at home with her and supports the Much Love charity's mission, says she can't help but open her home to needy animals. "I've always been that way," she says. "Ever since I was little I always brought home every little stray dog who didn't have a home. My daughters love animals as well, so I can't help it."
Richards' reality show, Denise Richards: It's Complicated
recently completed its second season on E!.