Nellie was typical of Marvel's girl-comics heroines of the time (which also included such characters as Millie the Model, Tessie the Typist, etc.) who were usually super-attractive, romantically complicated, somewhat befuddled career girls trying to make their way in life. Such comics were humorous in nature, with complications usually arising from the heroine's catching the eyes of various men, much to the anger of her current boyfriend.
Nellie was originally depicted as being a brunette, but at one point the artwork took a more manically-comic turn and the character was drawn as being a redhead (and decidedly more buxom).
Nellie dated Snazzy Wilks, a doctor; her best friend was Mary Lou, also a nurse, who dated a doctor nicknamed Speedy. Nellie's rival was glasses-wearing Pamela Lang, who constantly sought to catch Dr. Wilks's eye, although this usually ended up with her being humiliated by Nellie.
For her final one-shot appearance in 1957, Nellie was a blonde with a boyfriend named Don; Pamela was the only other holdover character from the previous incarnation.
Nellie the Nurse made appearances in other characters' comics, and similar Marvel characters also appeared in this title. Backup strips sometimes included Harvey Kurtzman's celebrated 'Hey Look!' strip.