I'm not sure I agree. Casey actually knew very little about her ZG, and most of what she did know did not match up with the ZG who viewed the apartment. Casey got the age wrong, the fact that ZG has children wrong, even the car wrong, I believe, because Casey said it was a 2008 Ford Focus and ZG says only that she drives a silver car. It's unlikely that a woman with no job, or a menial job, would drive a brand new car. Does the real ZG, not Casey's version, use the hyphenated F in her name?
It would certainly be a huge coincidence that ZG looked at the apartments where Casey claimed she dropped Caylee off, but it's also a huge coincidence that so many of these names show up in Casey's class roster. The names aren't all that common.
Can you imagine how shocked Casey must have been to learn that a ZG had looked at the SawGrass apartment IF she made the person up?