Don't Call Me Little Girl.

Joan Doubleday is a shy spinster, who has been engaged to Monty Wade for 12 years, is secretly adored by Peter Flagg. Her young niece, Jerry, arrives and sets out to capture Monty. On the wedding day, Jerry announces that the grooms have exchanged places and that Peter will marry Joan. A quarrel prevents preparations for the wedding, but Jerry finally convinces Joan that she was meant for Peter.