In a large mixing bowl, combine the fat-free sweetened condensed milk, fresh lemon juice, and lemon zest. Gently fold in the light whipped topping until smooth and well combined. Pour the filling into the prepared crust and spread evenly.
Refrigerate the pie for at least 4 hours or until fully set.
Before serving, garnish with additional light whipped topping, lemon slices, and zest if desired.
This makes 8 fluffy servings. Each slice is 14 WW Points. Enjoy!