movie on tv possibly 1950s about teenage girl killer

A widower suspects that his seemingly perfect adolescent daughter is a heartless killer.

Air Force Colonel Kenneth Penmark and his wife, Christine, adore their daughter Rhoda, despite her secret tendency for selfishness. Christine keeps her knowledge of her daughter's darker side to herself, but when a schoolmate of Rhoda's dies mysteriously, her self-deception unravels.

13-year-old Rynn Jacobs lives in a New England beach town. Whenever the landlady inquires after Rynn's father, she claims that he's not available. But when the landlady's son, Frank, won't leave Rynn alone, she teams up with a neighbor Mario to maintain the dark family secret that she's been keeping to herself.