Cook frozen berries in large saucepan over medium-low heat until berries begin to release juice, about 3 minutes. Increase heat to medium-high and cook, stirring frequently, until thick and jamlike, about 25 minutes (mixture should measure 2 cups – accurately measure this. If it measures more than 2 cups, continue to cook until it does – the pie will not set properly if you have more than 2 cups of the strawberry mixture.)
Combine lemon juice, water and gelatin in small bowl. Let stand until gelatin is softened and mixture has thickened, about 5 minutes. Stir gelatin mixture, sugar and salt into cooked berry mixture and return to simmer, about 2 minutes. Transfer to bowl and cool to room temperature, about 30 minutes.
Fold fresh berries into filling. Spread evenly in pie shell and refrigerate until set, about 4 hours. (Filled pie can be refrigerated for 24 hours.)
With electric mixer on medium speed, beat cream cheese, sugar and vanilla until smooth, about 30 seconds. With mixer running, add cream and whip until stiff peaks form, about 2 minutes.