The movie was about a little boy ( I think his name was Peter?)  that has a rough home life. Parents argued a lot. He meets and becomes friends with this little girl. They play together often. One day something happens (if I remember right an argument) and the boy runs from the apartment and ends up getting hit by a car. At this point it is reveled that the little girl is a ghost and and she wants Peter to choose to come be with her forever.  His mother sits in the street screaming and holding him. I saw this movie on the late 70’s while visiting my grandparents (I was probably 10 years old so my memory of events may be off some) and have never been able to find anything about it. It is driving me crazy! lol