In 2254, Nancy became romantically involved with Dr. McCoy; she even had a nickname for him, "Plum". Their relationship had broke off by 2256, but McCoy's feelings for Nancy remained unchanged for almost a decade.
Later, Nancy was married to Federation archaeologist Robert Crater. In 2261, the Craters arrived at planet M-113, where Professor Crater began a multiyear archaeological excavation of the ruins of an ancient and extinct civilization.
This character was only mentioned in dialogue.
In the final draft script of "The Man Trap", Nancy Crater was established as being an archaeologist, in common with her husband, though the final version of the episode leaves the impression she was a civilian instead.
The James Blish novelization, calls her Nancy Bierce. In the novel, A Choice of Catastrophes, Bierce is said to be her maiden name, while the comic Who's Who in Star Trek 1 says her maiden name is Pagano.
McCoy's relationship with Nancy happened while he was still married to but separated from his wife Jocelyn Darnell (β). A Choice of Catastrophes speaks briefly of it when McCoy is musing over his past.