I watched the 20/20 show and going off of that I don't think she killer her daughter. The marks on the child's face was more than likely done when CPR was attempted either by EMT, Mother or hospital. I know they all testified they didn't put the marks there but if you put that mark there would you admit it?
The girl was afraid of water however, I can also see a girl seeing bugs in the pool wanting to help them. (girl thinking if she is afraid so the bugs were too)
The mother while not model mother she clearly shows signs of loving them. The ending of the show tore me up because this mother had no idea her son was adopted. She still wished her son well.
Also since you passed the LD test, and wouldn't take a deal with the DA lends to her innocence.
The boy clearly wanted to please anyone he was talking to. My opinion is when he saw mommy trying CPR he confused that with killing her, possibly by direction from someone. TV show, cop, step grandad, interviewing him (cop stated he interviewed the child like he would anyone else)