Another possibility is George's sister or mother. Very early in this case, George's sister and his mother were at the Anthony home.
On July 16th, it was reported that the Anthony's were waiting for the police to return with Casey (when she led them on a wild goose chase), and monitoring their television as they expected an Amber Alert on Caylee. Someone called the Anthony house and told them to turn to a particular channel as it was being reported that Casey had been arrested. The article stated that at that time, George, Cindy, and George's sister were at the Anthony home.
On July 18th, George and Cindy did their first lengthy interview in their home. In that interview Cindy mentioned that her mother-in-law almost fell coming into the house because of all the media cables strung out across the front yard.
A few days later, George set up a card table at a supermarket parking lot and was passing out flyers. The local media showed George at the card table and a woman with a stack of flyers in her arms. She was identified as George's sister. For a week or two, George's sister was often with him when he set up a card table somewhere.
I would assume that George's sister lives nearby and visited George and Cindy on a regular basis. Like any other family, when there was a crisis, such as this one, she was there at the Anthony home along with George's mother.