Jacobs' (1988) paper entitled, "Euripides' Medea: A psychodynamic model of severe divorce pathology" views the Medea mother as "narcissistically scarred, embittered dependent woman...(who) ...attempts to severe father-child contact as a means of revenging the injury inflicted on her by the loss of a self-object, her hero-husband." Jacobs' idea that the Medea mother is so dependent that she cannot deal with the loss, and thus holds on with hate.
Medea certainly has a flaw in her superego. We know this early on when she betrays her father and kills her brother to help Jason steal from them. But she not only kills his new bride and her father, but her own children. Her love turned to hate is so passionate that she destroys that which intimacy between them produced. The hate goes beyond her instinctive need to protect her own children. Medea must make Jason suffer more than she suffers for it to be a punishment with revenge.
Jason, "You loved them, and killed them."
Medea, "To make you feel pain." (continue)