I have been back and forth on the Nanny issue. On one hand, this person could exist and others haven't met her if she were watching Caylee so her mother could party. Casey would not have allowed the sitter to contact her parents because she would not want her mother, Cindy, to know how often or how long Caylee was left. Casey was supposed to be taking care of Caylee, but could have instead been dumping her off on another person because Cindy gave her grief about being a mom and taking responsibility.
I agree with 2-Cents and brought it up long ago that she could be an illegal using a false name. One real ZG had a break-in and her laptop was stolen. However, I believe this was fairly recent and Casey contends she knew this person for a longer period of time. Research shows there are many Zenaida's across the country and we have no idea of the ones outside the country who could have "lost" their information. Tracking an illegal would be virtually impossible and the sketch then becomes crucial in an attempt to find her.
LE has taken the stance that Casey lied and won't forward the sketch to the public. They are not looking for the woman Casey claims to have her child. I think the lack of pursuing this avenue of investigation will prove to haunt them later on. If the woman happens to surface and did in fact watch Caylee, the defense has their out. The defense now claims other people did meet her and know she exists, but have offered no proof of this statement.
On the other hand...Casey could have made her up and it truly is just another lie spewing from her mouth as so many other things are untrue. Casey could have heard or read the name of the woman who blogs, for instance, as she seems known to the area. She is the one who was robbed. (Casey has also been accused of being a thief by her own mother and best friend. Did she possibly steal the laptop?)