Empty pie filling into a strainer to drain excess liquid, reserving some blueberries and liquid for garnish. In medium bowl, combine condensed milk, lemon juice and vanilla. Mux until well blended. Fold in whipped topping and mix well. Mound one third of mixture into crust and gently spread flat. Spoon a layer of blueberries over the mixture. Top with rest of mixture. Freeze until firm, about 3 hours. Let stand at room temperature for 15-20 minutes before serving. Garnish with reserved blueberries and liquid as desired.