Hugh Hefner has quietly added a new girlfriend to his posse. And she’s a “good girl.”

“I’m a good girl, for the most part,” new Hef gal pal Crystal Harris writes on her MySpace page.

The 22-year-old lesser-known girlfriend has frequently been photographed by the 82-year-old Playboy founder’s side, but never got a proper public introduction after former girlfriends Holly Madison, Bridget Marquardt and Kendra Wilkinson exited the Playboy Mansion.

Instead, fellow girlfriends – and 19-year-old twins – Karissa and Kristina Shannon nabbed headlines with their arrest records and, well, twindom, in the aftermath of the shake-up.

Harris introduced herself on an E! online message board over the holidays, telling fans that “Hef gave me permission to fill people in on the new updates as a voice from the mansion.”

No other girlfriends are in the mix at this time, she says, but “there are a couple that we have interest in. … As for now, it is just us three.”

Despite her low-key status, Harris already has a fan site, but seems to focus most of her attention on her MySpace page.

“I believe in opening your heart and letting your walls down, it is better to have loved and lost, than to never have loved at all,” Harris says on her site, which is peppered with Disney characters, cute animals, inspirational quotes and plenty of pink.

And, of course, the ubiquitous lingerie photos.

Harris hasn’t posed for her boyfriend’s magazine, but did appear in a series of topless and semi-nude photos as a Co-ed of the Week on Playboy.com in late October under the name “Crystal Carter.”

Pin-up moments aside, the 34-25-34 San Diego State University psychology student and PETA supporter lists “the rain, the seasons, fast cars, good food, volunteering, great company, caring and honest people, the ocean and animals” among her interests.

Harris was first spotted with Hefner – and the twins – in early October after Madison announced her split from the playboy, but has been cropped out of photos of the crew on more than one occasion.

E! has remained vague on whether they’ll renew hit series “The Girls Next Door,” which made Hefner’s former girlfriends reality TV stars, with the publisher’s new flames.