Bewitched (1964)

Season 6: Episode 18

Phyllis catches Samantha using her magic powers and doesn't really know what to think. So, after six years, Samantha finally tells Phyllis that she is a witch and gives her a demonstation of her powers. Phyllis tells Frank about Samantha, and she tries to show Frank, but her powers have been taken away! Because of all this, Phyllis commits herself to a nursing home, convinced that she is a lunatic.