Then why hide the body and not report it for 31 day
The woman has some obvious mental issues so she isn't going to react to any situation like a normal person would - that doesn't mean that she did it.
In any event, judging a person's reaction to a crime in order to determine their guilt is pure quackery - I don't know why that sort of thing is still allowed in evidence.
Casey did not enter a plea of insanity or mental incompetence or even mental deficiency so it is not up to the jury to decide her mental health. They MUST assume from lack of testimony to the contrary that she is mentally sane and healthy. I suspect some of them did decide their verdicts on facts like this that are not in evidence.
OK, then how does a child drown in a pool? At the very least you have negelect, and all the other crimes dealing with handling of a corpse/human remains.
She was examined by more than four shrinks.