Marianne Thorne was the main villainess from the made-for-TV film, Primal Doubt (alternately titled Personal Indiscretions).
She was portrayed by Jamie Rose.
Marianne Thorne was the therapist for Jean Harper, but she was previously the therapist for a woman named Amanda Freeman, who was believed to have committed suicide five years prior. In actuality, Marianne killed Amanda, who was having an affair with Jean's husband, Chase, and had been targeting Jean and killing those close to her, including Jean's best friend, Holly. Marianne turned heel and finally revealed herself to Jean at her home after killing Carla, all while donning an all-black outfit and brandishing a knife at her with intent to kill her.
Regarding her villainous motive, the evil Marianne ranted that she was tired of hearing privileged women complain about their little problems and wanted to show them what real suffering was, and she had that same intent for Jean. After her rant, Marianne lunged after Jean and attempted to kill her, but Chase enters and knocks her out. Marianne regains her composure and continues her attack, but she is later shot and killed by police officers.