I'm just saying and probably should have mentioned it in my earlier post that this is what may have initially started their argument....she didn't think about killing him ahead of time...no premeditation, no deliberation, IMO...
I certainly agree that the argument was about him going away with the children - even if he said it was only temporary, it sounds (from KM) as if she has a fear of abandonment so even JC taking the kids to Ireland for a brief birthday visit might have been too much for her to handle. If he had actually told her that he was leaving forever, that would certainly have sent her into the violent spiral... however, I wonder if Jason and her parents would have calmly gone to bed that night, knowing she had been given news that would have knocked her off her axis. Even for a woman who wasn't emotionally unbalanced, the news that her husband is walking out with both children and not coming back, would have been damaging enough that she would need someone to stay up with her. I can't imagine going to bed and leaving my daughter/ sister/ friend wandering around the house half the night after news like that.
And I agree that it wasn't premeditated, just a blind rage. If she had coldly and calmly decided to kill him so she could have kids and money, I think she would have picked a more plausible method.