IMO, this is about the clearest manifestation of true evil that even a Board like Websleuths contains.
This is not a Crackhead killing to support his needs, or a jealous spouse killing in fury over losing what is HIS. Or someone "trapped" in a marriage, killing to "get out."
The Krims never took anything from this Creature. In fact, they GAVE to her...they treated her like family...gave her money for trips. She had never been wealthy, but once she saw wealth, she felt ENTITLED to have it too. This is no serious mental illness...just the sickest manifestation of envy and jealously imaginable. This woman is vile beyond description. There are no excuses for her. None.
She came to hate Marina Krim, because she was not as fortunate as she. This is as sick as any type of senseless hate crime. But she was not content to strike out at the Mother, at an adult who might have had a chance to defend herself. No, she planned to "destroy" Marina Krim in the cruelest, most hideous way of all.
The most telling part of this crime is that she waited to see Marina's reacation. She dumped those babies, bleeding in the tub...and waited. Remember Marina had come up to the apartment once, looking for them, and then returned. She wanted the joy of seeing Marina's horror. This crime was not about the children...they were killed to hurt the Mother. They were not killed in a moment of rage and frustration...because she WAITED for her payoff of seeing Marina's indescribable pain.
In Marina's blog, only hours before, she wrote of how it was "almost cheesey" how much she adored her little boy. Reports say he was sleeping as his throat was cut. How calculating.
I wonder how long she and Marina were together before Marina left with Nessie for the swim lesson? She would not have left if the Creature was not behaving normally. But the Murderess was calculating...waiting to get those babies alone. Her life was not as GRAND as she wanted, she had spent money she could not afford, she wanted to BE Marina Krim...but, the next best thing was to destroy Marina Krim.
This is so sickenly premeditated...there is no punishment equal to the crime. Monster will not have to see her child slaughtered and live with that memory. She will probably just sit in jail, happily recalling the moment Marina walked into that bathroom...and delighting herself with thoughts of the pain that never leaves that loving Mother.