who killed her?

I must say I found the whole thing hard to swallow. Hardly a whodunnit, as the father is the prime suspect from the beginning, though he's so cool about it (with his actuarial tables and all). I thought for a moment, near the end, that there would be a twist and the daughter would turn out to be a nut job and her nightmares actually memories of what she had done.

And I find it hard to believe that the father would be able to plead the charge down to accidental killing - or that the daughter would accept this.