I don't know what you mean by this, CU... "What is 'O cup?" Did I make a typo that I'm not seeing?

And yes... I think that Strawberry Jello would work just fine. I'd use 1/2 a package... and omit the gelatin in the recipe. I doubt that using more water would be necessary... just use the same 1/4 cup to dissolve the gelatin that's in the Jello. Then before you put it in the pie plate, give it a taste to see if it's sweet enough for you. If not, add some Splenda.

Good luck to you! And please let me know how it turns out!