Casey could plead guilty to accidental death, but I can't see that happening. She's never had to admit guilt or take responsibility for her actions before, and I don't think she's about to take that step now.
I am not saying that she will plead guilty to accidental death because this isn't what she is being charged with. I simply saying that she will drastically change her story and say it was an accident and she didn't know how to respond and once again she becomes the victim.