For quite some time, it occurred to me that Casey may have just come home during the day when her parents were working, at least for some of the time.Children at that age usually take afternoon naps, which would leave Casey free to carry on her cyberspace life. But surely the neighbors would know if her care were there during the day.
The other issue which really still bothers me, is that if her irresponsible behavior was noticible, even in HS. Her lying & stealing became more pronounced after Caylee was born, why Cindy, as a mother, and particularly as a nurse, would not have sought help for her, boggles the mind. She's even identified her as a sociopath.
I think even Casey, somewhere deep inside of herself knew when she became pregnant that she was not capable of caring for a child, but was forced into it by Cindy, and the spiral then got out of control. She did make a cry for help to her friend by saying " she felt like she needed to get away for help," but that was never followed up on.