OK, so i have debating whether or not to post my theory on what happened here because I am somewhat of a newbie and DO NOT miss a Nancy Grace show, and cannot go one day without reading up on this case during my lunch break (of course I extend it a little longer to get as much in as possible)...but after this whole week of just thinking...I think I might as well..
I think that it is the obviously that at one point, Casey did love Caylee very much, as far as just about everyone saying how much a "Great Mother" she was and how she always had tons of pictures of Caylee on her facebook/myspace pages. Myself, being 23, knows that sometimes you change within the group of people that you hang around with (Not to mention how your parents are, you almost always carry those traits> ie George and the money issue, Cindy and the (sorry but true) lying and anger). I do believe that sometime in early 2008, Casey wanted to start going out more with this new group of friends, and Cindy just wasn't having it. This started to anger Casey, as Cindy would not watch Caylee as much, or always make her come home at night/early morning. Cindy started threatening Casey with taking Caylee away and filing for custody because she was an "unfit mother" in her eyes. Casey starts to do searches and starts to plot things out, a little bit a truth to it all, Cindy & George are fighting about a divorce. This is where the searches start to come in....She wasn't looking to kill Caylee, she was looking to put an end to her parents.(Telling AH that she could move in soon, her parents were moving/getting a divorce) . I believe that some things started to come out as far as how much Casey was doing behind her parents back (stealing money, partying). On the night she had the conversation with Tony (06/15 or 06/16 sorry I cant remember the exact night) She had told Tony she wanted to get away from her parents because of all the arguing about the divorce ( she wouldn't dare say "Oh my mom tried to strangle me") I think that she was planning to do away with her parents, as she didn't care for them, and was going to keep Caylee with her. The night of the unconfirmed fight, blew Casey over the edge with rage and anger, she probably took it out on Caylee. Scared, she didn't go home, and started to plan things about the kidnapping, using ZG as the kidnapper, whom we still do not know where this name came from...and probably never will, but what we do know, is that the real ZG does exist and Casey had to have connections to know as much as she did about her being at Sawgrass at that apartment that day.
Anyways, sorry for such a long post, I tried to keep it basic.....