A few things I don't understand
1. Did Rooney Mara actually expect not to be found guilty of murder and either sent to jail or a psychiatric ward for killing her husband? Or did she think that the worst that could happen is that she'd be sent to the psychiatric ward but released fairly soon after? Otherwise, I can't see why she would go along with the whole crime, knowing that she'd be going to the jail/hospital.
2. Why was Rooney Mara sent back to the hospital at the end of the movie? She just admitted that she faked being depressed and murdered her husband... so shouldn't be sent to jail (since she's not psychologically sick)?
3. Why did her confession to Victoria get Victoria arrested but not Rooney Mara, even though there's a similar confession to Jude Law which all of a sudden gets her arrested? In other words, how come Double Jeopardy worked to keep her from getting arrested when she confessed to Victoria, but not to Jude Law?