Brandi Glanville is opening up about an alleged affair her ex-husband, actor Eddie Cibrian, had with actress Piper Perabo on set of their 2005 film “The Cave”. The “Real Housewives of Beverly Hills” alum claims the two were “f**king” behind-the-scenes.

“They did a movie together and [my son] Mason was 1-year-old and I went to the set and it was in another country, Romania, I think,” Glanville, 50, recalled in a new interview with Page Six.

“And [Perabo] was a horrible c**t to me,” she added.

READ MORE: Brandi Glanville Sends Love To Ex Eddie Cibrian And His Wife LeAnn Rimes After Missing Thanksgiving

The “Unfiltered” podcast host explained how she became uncomfortable at the sight of her ex and Perabo, given what she knew about the alleged interactions between them.

“She was flirting with Eddie, like, right in front of me,” Glanville claims. “I was like, ‘Am I here? Am I the only person [seeing this]? Like, what is happening?’”

Glanville, who tied the knot with Cibrian back in May of 2001, noted that she “made friends” with “The Cave” crew members who kept her in the loop about things that were happening on set and “heard a lot of things.”

The Drinking and Tweeting author claims she was informed “that Piper and Eddie were f**king.”

When Cibrian returned to the former couple’s Los Angeles home, after filming had wrapped, Glanville claims she confronted him about the alleged affair.

“When he got home, I’m like, ‘I’m leaving, blah blah, I’m out,’” she shared.

READ MORE: Brandi Glanville And Ex-Husband Eddie Cibrian Gather Together To Send Son Mason To Prom

“He convinced me that it wasn’t true,” she continued. “We had a 1-year-old son and he was the love of my life at the time and, you know, there was a lot of convincing me of things.”

According to Glanville, Cibrian dismissed her concerns, telling his then-wife that she was “just crazy” and “jealous.”

“And I was like, ‘All right.’ I was in love,” she said of her decision to stay by Cibrian’s side. “Like, I was blindly in love with the man.”

Glanville and Cibrian welcomed their first born, Mason, now 19, in June 2003. For a period in 2004, Cibrian resided on location between Romania and Mexico where “The Cave” was shot. The two also share a younger son, Jake, 15.

Following Cibrian’s alleged involvement with Perabo, he was entangled in high-profile affairs with “Vanderpump Rules” star Scheana Shay and country singer LeAnn Rimes. Despite the actor’s months-long relationship with Shay in 2006, Glanville continued to stand by him until his 2009 affair with Rimes. The pair eventually got divorced in 2010 after nine years of marriage. Cibrian is currently married to Rimes, who he wed in 2011, just two years after meeting her on set of Lifetime’s romantic-drama “Northern Lights”.

READ MORE: Brandi Glanville Recalls Telling LeAnn Rimes ‘I Will F**king Murder You’ After Singer Cheated With Eddie Cibrian

“It’s kind of ironic that [Perabo] was in ‘Coyote Ugly’ with LeAnn,” Glanville told Page Six of the 2000 blockbuster that was made long before they each met Cibrian. “I’m like, ‘Oh gosh, they shared the same D.’”

Glanville, who stars in Peacock’s upcoming competition series “The Traitors”, added that she’s neither a fan of “Coyote Ugly” or Perabo.

“I don’t like her as a person,” she said, “because I think she f**ked my husband.”