Mix graham cracker crumbs with melted butter. Firmly press this mixture into the bottom and about 1 inch up the sides of an 8-inch or 9-inch springform pan.
Using an electric mixer, beat cream cheese in a large bowl until it becomes smooth.
Beat in 1 1/2 cups powdered sugar, lime juice, lime zest, and vanilla until the mixture is smooth.
In another bowl, whip the cream with an electric mixer until stiff peaks form. Gently fold the whipped cream into the cream cheese mixture, taking care not to deflate it. Taste and adjust sweetness if needed.
Transfer to the prepared pan, cover, and refrigerate for at least 5-6 hours or until set. Slice and serve with sweetened whipped cream as desired.