This was a tv show episode.

I think it was from the late 90s or early 2000s.

I cant remember if the series itself was comedic, or if I just happened to stumble with a comedic episode.

A therapist was manipulating her patients, and, in some times, also seducing them.

A group of investigators tried to plant people in order to expose her.

During the final scene, it was revealed that the old man working at the agency was also one of the people who were able to score a point and have sex with the therapist.