She Wrote the Book (1946)

"She wrote the years BLUSHING best-seller... then had to live it... page by burning page"

A plain-Jane math professor (Joan Davis) at a small midwestern college is talked into journeying to New York on behalf of a colleague who has written a steamy bestseller under an assumed name. When she arrives she gets a bump on the head which brings on a form of amnesia and she begins to believe she is the author of the book. Hijinks and adventures follow.