The thing with Sophia is that I *knew* she had turned and she was going to show up at some point, especially once we found out what was in the barn. She had to have been turned once a day passed on the show because if she hadn't then the zombies were no longer a credible threat if an 8-year-old girl managed to avoid them and not get bit after DAYS. Weeks, likely, given the recovery of Rick's kid and him changing to a little shit that needs a good smack across the head.
It seemed to me after a while every episode was this:
Rick: "We need to find Sophia!"
Shane: "We need to get movin'!"
Hershel: "You need to get off my land!"