Where wild minds come to rest
I saw this on AMC with Marilyn Monroe. She was supposed to be baby sitting at a hotel and kept spacing off into fantasies with this pilot who was on a different floor of the hotel. He kept rejecting her advances and each time he did it sent her deeper into daydreams of them getting married. She was wearing some other woman's clothes so she could look more wife-like. At the end of the movie she was knocked out or something, while she was on the floor she had a whole scenario in her with the two of them living happily ever after with kids. As the movie goes off she couldn't stop it.
Have you seen this movie?
There is also a British version of this made in 1961.