She was a carryover character
May 8, 1943 - Dr. Gillespie's Criminal Case released (USA).
Dr. Gillespie's Criminal Case is a 1943 film in the Dr. Kildare series. Based on characters created by Max Brand, it is the third of six films in MGM's Dr. Gillespie series. The series went from 1942 to 1947.
Donna Reed's character originated in the film Calling Dr. Gillespie, the previous installment in the Dr. Gillespie series. A Variety review mentions Donna as a carryover in the series but her performance is not commented on.