My prediction for episode 6: A wounded Reeva battles Owen and Beru on Tatooine while Obi and Vader battle on Mustufar. Owen kills Reeva.
They needed another action sequence to cut into and out of during the final battle. Star Wars always intercuts the final battles. They even forced intercuts during episode 3 Obi/Vader fight with detective Reva and I hated it!
The only reason Reeva is still alive is for this purpose.