How Ariana Madix Learned Tom Sandoval Was Cheating on Her with 'Vanderpump Rules' Costar Raquel Leviss

Ariana Madix discovered Tom Sandoval was cheating on her with fellow Vanderpump Rules star Raquel Leviss upon seeing a racy video, according to sources.

News broke on Friday that Sandoval, 39, and Madix, 37, split because the TomTom Bar co-owner allegedly cheated with their costar.

Madix learned about Leviss and Sandoval's alleged affair on Wednesday. That night, she was at a venue in Los Angeles supporting her then-boyfriend's band, Tom Sandoval & the Most Extras. The two were spotted by onlookers kissing.

While there, a selfie video that was sexual in nature from Leviss popped up on Tom's phone.

Madix then began scrolling and saw their history of inappropriate texts.

"This has been going on for upwards of 6 months — all the while, Tom was sleeping next to Ariana in bed," one source told PEOPLE. "She was completely blindsided by this; devastated doesn't even scratch the surface of how she feels."

"This is someone she thought she knew; someone she planned to spend the rest of her life with. You can't even put into words that betrayal," the source added.

"She was supporting his new single," a second insider said of Madix being at Sandoval's show on Wednesday. "She had no idea any of this was happening behind her back."

Also on Wednesday, on the other side of the country, Leviss made an appearance with Scheana Shay on Watch What Happens Live with Andy Cohen where she defended her decision to kiss Tom Schwartz, Sandoval's best friend and business partner.

"I'm just trying to live my life and I'm sorry if that offends people but it's not going to stop me from doing what I'm going to do," Leviss said, later giving Andy Cohen a TomTom sweatshirt as a gift.

After the taping, Leviss admitted to Shay the truth about her and Sandoval, a third source told PEOPLE.

"Scheana was furious," the source said. "She and all the Vanderpump Rules costars have rallied around Ariana during this time. They can't believe Raquel would do something like that."

A fourth source told PEOPLE earlier on Friday that Madix and Sandoval had been having problems "for a while" but that learning of this "was the final straw for Ariana" after nine years together.

"She put up with a lot over the years, but she won't sit back and be disrespected this way," the insider said.

Madix, Leviss and Sandoval could not be reached for comment, and have not publicly addressed the allegations.

Fans will likely see the drama play out on season 10 of the Bravo series, which is airing now.