So she's been declared not guilty. Okay. Why is this a problem? How, exactly, does anyone know that she actually did it and "got away with it"?
Personally, I'm kind of sick of people acting like being accused of a crime is the same as being guilty. I agree that the details of this case seem a bit fishy, and Casey seems like she was a terrible mother, but there is no proof that she killed her daughter. No cause of death, no nothing.
If the jury says she didn't do it, then barring any new evidence, I see no reason to question it (aside from the very human desire to cast blame in order to make oneself feel better).