Madix and Sandoval dated for almost a decade before TMZ reported in March that Sandoval and costar Raquel Leviss — Madix's former best friend — were involved in an affair.
The pair's relationship was uncovered by Madix after she found a sexually explicit video of Leviss on Sandoval's phone.
Appearing on "What Watch Happens Live" after the finale had aired, Madix was asked by Andy Cohen about Sandoval's apology.
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"I thought it was laughable," she said.
The 37-year-old reality star also hit out at Sandoval's best friend Tom Schwartz for "covering" up the affair and "actively participating in my downfall."
Madix said it was difficult to watch back the season because of "the fabrication of a narrative that was being formed the entire time without my knowledge, behind my back, by not just my ex-boyfriend but his little flying monkeys, as well."
"Tom Schwartz, mainly," she then said.
Asked if she had any suspicions of Sandoval and Leviss' affair, Madix said that she did feel that something was off with Sandoval in the months leading up to the news of the affair becoming public.
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"It's like, I wasn't suspicious about an affair or about Raquel, but I was, like... something was clearly going on with him mentally, and that is what I was picking up on," she said.
Describing Sandoval's reaction to her finding out about his affair with Leviss, Madix said: "From the moment I found out, he was screaming at me. We were in the backyard and he threw a beer can ... he was more concerned about people hearing at TomTom than how I felt at all."
"I think there's some part of him that's really loving the attention that this has brought him, and as long as people continue to give him that attention, he will be happy about it," she added.
Asked if she'd forgive Sandoval and Leviss, Madix said: "That's not happening."
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