If anyone knows this movie?

ok sooo...
I remember it is very old,and it is about a girl that lives in a small town,and her mother forces her to date older man in hope she marries rich,and than comes this younger guy in the town and takes her in the end with him but her mother finds her somehow and wants to live with them so she ends up killing herself...and then they show her little sister in her dress talking to this boy somewhere on the railroad in her older sisters dress...ok so that's it...anyone???

The movie is This Property Is Condemned (1966). Older sister - Natalie Wood, younger sister - Mary Badham, young guy - Robert Redford. Director - Sydney Pollack (one of his best works).