My take on that is if that is the case, she's got a lot more to hide than just losing or killing her daughter. From what I've seen on the net over the past couple of weeks and looking through all the pictures, I have a feeling that this girl was into something very, very, very sinister (gangs, cults, drugs, porn, etc.). And if that's the case I think GM & GP either knew about it or found out which is why they won't say or don't know who the dad is of Caylee, and why they never asked questions of Caley on her comings and goings at all weird hours of the day and night and being gone for days on end.