Can you name this movie?

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I've been racking my brain for the title of this movie. I remember watching it when I was younger. My guess is that it was a drama. The style of dress makes me think it was made in 1979-80. Here's what I can remember. It starts out with an adorable little girl who's maybe 6 or 7 years old. She and her parents live in a big fancy house. I remember thinking that the family was wealth. Her parents are having some sort of dinner party. She feels neglected or forgotten and writes a letter saying she's running away. The letter falls down behind the dresser or something. She ends up hiding in the back of a station wagon sort of car and then two men come along. One is tall and thin and the other is a little shorter and stalky. They decide to steal the car (I think) and do so. Later, they find the little hiding out inside. They decide to try to ransom her. While they're trying their best remain at their objective (getting the money), the stalkier guy starts to warm up to the little girl. Then the tall thin guy starts to also. I remember they buy her a puppy at one point and an ice cream cone. They're outside and she's feeding the puppy some of her ice cream cone. At the end of the movie...they care deeply for her and forget about the ransom, they just want to return her to her family. They agree to meet at some sort of ski resort or something..I remember there being ski lifts. The ending scene is her parents holding her and she's crying and waving at the two guys who are being driven away in a police car. If anyone can remember this movie and it's name I'd appreciate it more than you know. It's been driving me crazy!