Just as Andrea finally freed herself from the dental chair, zombie Milton lurched at her. Then, the camera scene switched to outside the room, and all viewers could hear were the sounds of the attack and struggle. However, that’s not originally the way it was intended to go down. It turns out that The Walking Dead Season 3 Finale went through reshoots.
Now, thanks to an AMC behind the scenes video, we actually have images of how the Milton attacking Andrea scene was originally shot. In the first take on the scene, Andrea was actually bound to the dental chair by heavy chains. She did not free herself before Milton attacked.
In fact, Milton quite graphically bit into Andrea’s side, and Milton reared back his head with blood dripping from his mouth. Keep in mind, this scene isn’t just showing what happened behind the closed door, but it represents a completely different death for Andrea.
If Andrea was originally still chained to the chair when Milton attacked, then it wouldn’t have allowed for the suspense of Rick’s group entering the room and slowly discovering Andrea had been bitten. If Andrea was still chained to the chair, it’s also likely she would have been devoured by Milton. Andrea wouldn't have been in a position to commit suicide to avoid turning into a walker, like what happened in the version of the finale that actually aired.