Is Angelika Graswald’s purported confession a little too convenient for prosecutors?

Angelika Graswald (previous posting) is on trial for murdering her fiance in order to pocket the life insurance proceeds. The main evidence against her is stuff that she supposedly said to a police investigator (nytimes; ABC News). Does this make sense? Here’s a woman from Latvia who figured out how to work the U.S. immigration system, marry and divorce twice at a profit, and arrange for life insurance on her fiance. Then, two weeks after the drowning, she calmly gives it all up with a justification of incipient domestic violence? This recent New Yorker story describes the criminal justice system in New York as somewhat less than straightforward (consistent with the lectures on Forensic history that I wrote about in March). On the other hand, the police have at least some of it on video.