Her Highness and the Bellboy (1945)

In a fictional European country, a beautiful princess meets a handsome American reporter and falls in love with him. On a trip to New York, she hopes to find him again. While staying at one of the city's finest hotels she meets a kind-hearted bellhop who mistakes her for a maid. She invites him to be her escort, not realizing that he believes he has fallen in love with her. Every nice thing the princess does encourages him to believe that she feels the same way he does.