I agree that chopping up a body sounds over the top to most of us (although there have been cases on websleuths where husbands have cut up the wifes body for disposal) but again I am asking how the body could have been disposed of. I do not think there could have been any blood in the apartment or the parents might have already been arrested. So if, as you believe, the girl passed away from overdose of meds or complication of meds they still had to chance moving the body of a 3 yrs old to dispose of it and then at a certain time to raise the alarm "they've taken her!" If the body had been found anywhere with too much meds in it this too would have pointed at the parents and that would be as unacceptable to them as her body being found in her room with the meds in her.
At this point the scenarios for the body being disposed of by the parents seem unlikely at best. Could a friend have helped by disposing of the body? I suppose so but I suspect L.E. has looked into all those possibilities.
At this point it would be far a simpler scenario for someone else to have walked into the room and just taken the child away to raise, sell, or rape and kill and dispose of the body far enough away from where everyone was looking to have it go undiscovered this long. The child could have been carried away like any other child or could have been placed in a bag, a rug, a clothing hamper or even an ice chest on wheels and carted out past everyone.