Linda Carter began life as the star of her own romance comic where she was a student nurse.
Linda Carter was created by Stan Lee and Al Hartley first appeared in Linda Carter, Student Nurse #1.
The history of the Night Nurse is one fraught with confusion. There have been many characters who have being identified as "Night Nurse", and possibly even more than one whom was named as "Linda Carter".
Linda Carter was a romance comic book star similar to Patsy Walker and Millie the Model. Years later in a series called Night Nurse, one of the three titular "Night Nurses" was called Linda Jane Carter. Other than the name and profession, any connection was assumed by readers rather than stated - although the only refutable evidence is that the two have different hair colors.
Brian Michael Bendis began using a Linda Carter as the de-facto "Night Nurse" character in his Alias and Daredevil books and subsequently used the character in The New Avengers where it was confirmed she was the same Linda Carter as the Student Nurse rather than the Night Nurse Linda Jane Carter. To make it even more silly, Linda Carter was now sporting a different hair color to both previous Linda Carters.