On Episode 23: Hell's Kitchen Kelsey tells Sierra all about the horrific crime that Katherine Mary Knight committed and the behavior that led her down a dark path of domestic destruction. 

Sources:
Deadly Women Season 1 Episode 3: Revenge
https://en.wikipedia.org/wiki/Katherine_KnightV
https://www.nydailynews.com/news/justice-story/aussie-woman-removed-beau-skin-article-1.1476480