In a medium sized bowl, blend the cream cheese, cool whip, powdered sugar, lime zest and lime juice with a handheld mixer until combined. Fold in the chopped blueberries. Scoop the cheesecake mixture into a plastic bag (it might be runny and messy, so be careful), cut off the corner, and pipe the filling into the cups on top of the graham cracker crusts. Top with extra blueberries, cover with plastic wrap, and refrigerate for a couple of hours to overnight, just to help it set up. If you eat these cheesecake cups immediately, the texture will be more like yogurt instead of puffy no-bake cheesecake. Keep stored in the refrigerator for up to 7 days.