Frankel took issue with de Lesseps' approach to sobriety and for not supporting her after her boyfriend Dennis Shields' death.
"It was an explosion and a reaction to many things," Frankel told host Andy Cohen.
"There was a boiling point. But there was really something that I was observing in her that was really triggering me."
"I just, I had had it," she said.
"I just felt like, 'What the hell? Who are you? How are you so not self-aware?' And even right after that moment, she was like, 'Well, I've been going through a lot.' I don't want to be like, 'I've been going through a lot,' but I've been through a little bit this year."
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Frankel said she's grateful people seemed to understand where she was coming from.
"It popped off. It seems like people understand it. I felt terrible about it," she said. "I felt really just unhinged, but everyone got it."
Frankel said she's no longer helping de Lesseps with her personal issues.
"I'm out, but I would do it again if something really bad happened, because I would do that for anybody. But I like this distance from the situation," she said.
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