Would the meaning of a sentence changed if I say "meal" instead of "treat"?
Yes, I believe it would change the meaning. "Meal" indicates a dinner or lunch, something that you get every day. "Treat" usually indicates a dessert, especially since she brought out a pie. Using the word "treat" means food that you don't get often. Ex: She made the kids a special treat: chocolate chip cookies! Ex: I want to stop at the gas station for a treat.