How we cite our quotes:
Medea: My heart dissolves
When I gaze into their [her son's] bright irises […]
Why damage them in trying to hurt their
and only hurt myself twice over? (173)
Besides betraying her sons, might Medea also be betraying her self in some way? Though she's doesn't seem too upset about killing her sons, she does a good bit of crying about it beforehand. You could look at it like her destructive side is betraying the gentler side of her nature.
Medea: What power or divine one is ready to hear you [Jason]:
perjurer, liar, treacherous guest? (225)
Medea feels that the gods are on her side. In her mind, she's only bringing justice to the situation. Jason betrayed her and he deserves what he gets. The play seems to support this idea. Medea receives no divine punishment for her actions. In fact, she gets away on a chariot once given to her by her grandfather Helios, the sun god.
Jason: I'd rather they'd never been born to me
Than have lived to see you destroy them this
To the end, Jason is completely unrepentant of his betrayal. Notice that he doesn't say he wishes he'd never taken another wife. Instead he says that he wishes his children had never been born.