Her behavior was so out-of-place that the jury may not have known what to deduce from it. It almost looked like she didn't even know that Caylee was dead. It doesn't seem to serve as evidence of anything in particular.
It makes no sense whatsoever that someone is not looking over their shoulder for the cops if their child just died, however the child died. Even if one looks at her personality and motivations to be me, me, me, it's all about me, you would still look for someone to get really nervous occasionally.