On a personal level, it has happened to me that I vented to a friend about something that someone had said or done to me that I was upset about (which is permitted under certain circumstances). The friend’s reaction was to criticize the person and make negative assumptions about them. It was fairly similar to what was done here. Her comments did affect the way I thought about the person as well as how I related to her.
I realized after that that this friend is probably not someone whom I am allowed to vent to according to Halacha. You are supposed to choose someone who will not be “mekabel” what you say and certainly won’t add to it!