She did display shock when she was shown pictures of her deceased daughter. Perhaps after lying to herself for so long she finally accepted the truth.
Unfortunately we will never what thoughts were running through her mind or how sane she was and became after her daughter was missing.
It seems like her family itself was very messed up and being raised in that family didn't allow her to develop correctly in her mental capacity.
That’s too far-reaching for my common sense. Go watch the trial. You’ll see.
Please see post #75