My Sister and I (1950)

The rich, aristocratic Katarina Hassel decides to let an architect renovate her mansion. Katarina falls in love with the young architect, Gunnar Stenwall. Alas, he doesn't fall in love with her. But perhaps if Gunnar would meet her identical sister, who works in Stockholm, he would fall in love with her. So Katarina travels to Stockholm to act as her non-existing sister.