Former "Real Housewives of Beverly Hills" star CAMILLE GRAMMER is a "homewrecker"!

That's the shocking claim of LISA CHYNOWETH, who says Camille's current beau — Dallas attorney DIMITRI CHARALAMBOPOULOS — was living with her and their young son when he and Camille began their affair.

What makes the situation so ironic is that Camille publicly criticized ex-husband KELSEY GRAMMER for cheating on her with his current wife, KAYTE WALSH, while she and Kelsey were still married — and now it's Camille who's the "other woman"!

"It's a case of the pot calling the kettle black," said an insider. "Camille's being accused of doing the very thing that she accused Kayte of doing."

Although they never married, Lisa and Dimitri lived together for several years and have a 9-year-old son. In 2010, Lisa moved to Colorado for a short-term job commitment, leaving the child in Dallas with Dimitri.

But according to court documents, Lisa gave up the job and returned to Dallas on the condition that she and Dimitri would finally tie the knot.

Those plans fell apart less than a year later when Dimitri, who also worked as a personal trainer, accepted a two-month training gig in Malibu.

"At the same time we were together…in Dallas, he deceived me and my son and was having an affair with Camille Grammer," Lisa stated in court papers she filed, requesting permission to return to Colorado with their son.

Dimitri is challenging the move and has requested the boy remain in Dallas, even though HIS address is now listed on the same street that Camille lives on — in California.

Lisa also claimed that Camille called her on Jan. 18, 2011 and threatened to "desecrate" her if she told her story to the press.

But the tables could turn on Camille once again.

"Camille needs to watch out," warned the insider. "She's certainly not the first older, rich woman Dimitri has dated — and she won't be the last!"