ok just some stuff of teh top of my head (i did this now 2 years ago so dont expect amazingly accurate references to quotable everyones, but joys i happen to be an ancient history major)
Greeks did not hold women in great esteme. Aristole, a very famous greek philopher once claimed women to be a "miosgotten man" they were denied citizenship with a polis and were cloistered away from men. they could not divorce their husbands. Greeks believed teh prefect polis (city-state) was full of men, they were suspisious of women, regarding them as evil (pandoras box) and distrusted them immensly, believing without men there to guide them and keep them firmly in check they were capable of evil deeds
Eurpides reflects how this inequity could lead to disaster. Like all revenge tragedy hero Medea is trapped in a system wrer she can rcieve no justice. In this case it is because fo two reasons. One aKing is in charge, this would have been particularily acceptable excuse for an Athenian as Kingsw ere veiowed as Tryants for the most part, despised by athens and the anthisis of the greek democarcy. So because Cleon wished for his daughter to marry Jason Medea had no choice. She could not go against teh wishes of the the king of the country in which she was staying.
Sercondly Jason had every right to divorce her. The choral ode
(technique, common in teh period of for the medium of drama) is strong is supporting womens rights, stating how if women could write teh stories how very different theyd be. It goes on to show how despite medea giving up everything for Jason and saving hsi life, as a women shew as nothing to him. She had no way of appealing the decision to justice so she moves outside of that sytem to teh feild of personal revenge.
Also the inate distrust of Barbarians that contextualised teh Greeks is evident within the play. medea is ostricised beacuse she is a foreigner, futher developing the convention of being outside teh social system. She is distrusted, and teh use of her "majic" and deciet, and use fo poisen are all common ways of affirming this contextual apprehensions.
anyways at some stage ill put somthing better up when i have a chance to think about it. This link gives you a very good overview with context
http://www.gradesaver.com/ClassicNotes/Titles/medea/fullsumm.html
but just read the analysis section