I think she will blame her parents. Both of them.
They had Caylee, her dad told her he would pick the car up from Amscot ,he didnt he put Caylee in the trunk because Cindy killed Caylee. Then the car was towed and Casey wasnt worried because she thought her parents had Caylee and the car,because they take care of everything. Except Cindy has fits of rage and Caylee was hard to handle and Casey thinks her parents set her up and when she was made to leave tony's and go home they told her what to tell the cops,because they wanted to blame her only she didnt know that then they told her Caylee was alive and it was for a money scheme.But really they wanted to ruin Casey like she ruined them . She ruined their retirement years making them raise a baby doing what she wanted and stealing from them. Her parents hate her.
Her parents framed her. That why they asked her to lie about the nanny. and all those other things. Of course she doesnt know the details she wasnt arround but they did ask her to lie and they did have Caylee last.
I hope he knows no jury will buy this but I do think this is going to happen. Casey doesnt care about her parents at all and it motivated to only do things that benefit herself. He just needs reasonable doubt so that might be all he is aiming for. If he tosses enough crap in the air he is hoping some will stick to the ceiling.