Should I tell Denver Kris has been talking about her?

Denver and Kris became friends through their spouses a couple of years ago. When Denver separated from her spouse, Denver dragged her through the mud by talking badly about her and spreading lies. Kris even stopped speaking to her by ignoring her calls and emails. A year later, when Denver and her spouse got back together Denver reached out to Kris and they started talking again. Denver has no clue the vicious lies Kris spread about her. Should I tell Denver or just leave it alone.