we don't really know that for sure, that's only speculation. i think it could be something totally different than that, personally.
the only 'huh' i have that no one else has said is the fact that CA had no connection with the 'nanny' whatsoever, but for a different reason than just 'she's her grandmother, she should know the child's baby-sitter.'
i find it very hard to believe that casey would never have asked her parents to pick up or drop off caylee at a baby-sitter's, claiming to work late or whatever other excuse she could think of to get out of her responsibilities. no way. she shirked everything else, but always managed to get caylee from the sitter on time? please.