Bride by Mistake (1944)

The staggeringly wealthy Norah Hunter, a shipyard owner, too often finds herself the romantic target of gold-digging men. To attract a suitor whose main interest is not money, she changes places with her secretary, Sylvia Lockwood, and assumes the role of a young working woman. However, she then falls for recuperating fighter pilot Anthony Travis, who, in turn, is madly in love with Sylvia -- or, perhaps, with the millions he thinks she has.