i believe there should be 3 to 4 webisodes based on Sophia's last moments something like this
Ep1: from episode 1 of season 2 Sophia running away from road hides Rick follows and kills walkers before Sophia ventures back towards the road.
Ep2: Sophia wondering the woods lost then finds the abandoned farm. Goes into the kitchen and eats the tuna before going upstairs to grab and pillow and blanket and going to sleep in the pantry
Ep3: Sophia waking up and venturing out the farm house and begins walking again. She stumbles across that stream where Daryl find her doll. She's spoted by a walker and runs falling over the log and lossing her doll. The walker catches up to her and bites at her neck. Otis kills the walker. And watches Sophia die in his arms.
Ep4: Otis has attached the pole stick around her neck and she wakes up as a walker. Otis takes her back to the barn with the Greene family watching besides Jimmy who helps him put Sophia into the barn. Before Otis tells the that his going to wash up, reload his gun and go hunting.