After the way that Lisa Rinna treated Denise Richards during The Real Housewives of Beverly Hills season 10, it comes as no surprise that the two former friends became involved in a nasty feud. Denise Richards was brought onto the series at the start of season 9 as a friend of Lisa Rinna's. The two began their 20-year friendship when they both started out in the entertainment industry. Specifically, they met during the early days of their careers, when they were both models and later worked together on the set of the Good Advice movie. Up until RHOBH season 10, Lisa and Denise's friendship seemed to be unbreakable.

Little did they know that a simple rumor would cause the end of their longstanding friendship. Last season, former Real Housewives of Beverly Hills cast member Brandi Glanville revealed to Kyle Richards and Teddi Mellencamp, who left the series last fall, that she and Denise had a romantic night together while visiting Denise on the set of a movie. When Teddi relayed the news to Denise at a dinner during their cast trip to Rome, the actress firmly denied the claim. However, many of her castmates, including Lisa Rinna, refused to believe it. Here is a timeline of Lisa and Denise's ongoing feud.

Related: RHOBH: Garcelle Beauvais & Lisa Rinna's Feud Timeline

Denise Richards' First Lie

Denise Richards on The Real Housewives of Beverly Hills promo shot

The feud between Denise Richards and Lisa Rinna ignited when Denise lied about her daughter, Lola, getting offended by the women talking about threesomes during a party at her home. Lisa, who is also in a feud with Garcelle Beauvais, was confused as the 50-year-old has been very open about her past sexual activity on camera. Denise tried to explain to Lisa, who is the creator of Rinna Beauty, and the other women that she doesn't mind opening up to the group, but not in front of her children. However, in a scene between Denise and her daughter, Lola does not appear to be affected at all by the threesome talk.

Denis Richards' Affair With Brandi Glanville

Denise and Brandi smiling on a golf course in RHOBH

While getting ready for their trip to Rome, Kyle and Teddi were told by Brandi that she and Denise had slept together shortly after they met the year prior. Kyle seemed to believe Brandi, adding she's never known her to be a liar. Once they got to Rome, Teddi blurted out the rumor that Brandi had divulged, which Denise adamantly denied. She even called Brandi nothing more than an "acquaintance." Later in the season, Brandi denied that she and Denise were only surface friends by showing texts to prove they had a close relationship. When Lisa saw the texts, she realized that Denise was lying to her and the group.

Lisa Rinna Confronts Denise Richards At The Reunion

RHOBH's Lisa Rinna and Denise Richards posing together

During the Real Housewives of Beverly Hills season 10 reunion, Lisa Rinna wasn't afraid to attack Denise Richards about lying the whole season. She called her out for lying about Lola's feelings regarding the threesome conversation, as well as her friendship with Brandi. Lisa also wasn't happy about Denise sending a cease and desist to Bravo, her RHOBH castmates, and even Brandi. Lisa believed Denise was gaslighting the cast the whole time, leading her to regret ever asking Denise to join the show. In turn, Denise felt that Lisa had thrown away a friendship of more than 20 years to stir up some drama for a TV show.

Shortly after the season 10 three-part reunion had aired, Denise left Real Housewives of Beverly Hills for two seasons. More than anything, Denise was hurt by Lisa's attacking her the whole season when she should have just been a friend to her. Lisa has admitted to being too harsh on Denise last season, but don't count on reconciliation between these two anytime soon. Denise has moved on from the tumultuous season, but she will never forgive Lisa for how she tried to destroy her image.

Next: RHOBH: Andy Cohen Denies Erika Jayne Refused To Appear On WWHL

The Real Housewives of Beverly Hills airs Wednesdays at 8 pm EST on Bravo.