Ending?
As I remember it, when Lassie arrived, they tried to feed her, but could not, due to her being so starved her digestion would not function. I don't remember them ever feeding her, or saying something like 'The vet will fix her' or 'Try some soup' or something.
As they left it, the dog could have just starved to death. Does anyone have a different view, or memory of what happened?