Key Lime Pie: To. Die. For. In a large bowl, dissolve one 1/16 oz. package sugar-free lime gelatin gelatin in ¼ cup boiling water. Stir in two 6oz. key lime pie yogurts with wire whisk. Fold in 8oz. fat-free whipped topping with wooden spoon. Spread in reduced fat graham cracker crust. Refrigerate for at least 2 hours.