(written from a Production point of view)
Barbara Baldavin (born 18 October 1938; age 75) is an actress who appeared in a handful of smaller roles on TV and feature films between 1966 and 1993. Best known for her role as Nurse Holmby on the TV show Medical Center, Baldavin is the wife of casting director Joseph D'Agosta and later became a casting director herself. She appeared in four episodes of Star Trek: The Original Series.
When Baldavin was called back for a subsequent appearance in "Shore Leave", her character in the script was called "Mary Teller," but crew on the set realized she had played a major character named Angela, so she was called that in dialog. However, Shatner still calls her "Teller" at one point. Later, when she had a small appearance in "Turnabout Intruder", her character was called "Lisa" in the script and referred to as "Lieutenant Lisa" in one line by Shatner.