More later, but I'm fascinated by the shifting focus of blame from Medea (in the Heroides) to Jasoun (in the Legend). Chaucer mentions blame of Medea twice, very briefly: when he directly refers to Hypsipyle's letter, he mentions that Medea "had his herte y-raft hir fro," and almost curses him to his later fate of Medea (unmentioned in Medea's own legend), praying that Medea "Moste finden him to hir untrewe also, And that she moste bothe hir children spille" (1572; 1573–4). In fact, the earlier portion of Hypsipyle's legend is focused on Jason's own blame in his seduction and betrayal of her, saying that "Betwixe him Jasoun and this Ercules. / Of these two here was mad a shrewed les / To come to hous upon an innocent. / For to bedote this quene was hir assent" (1543–1547).
In contrast, the Heroides focuses much more heavily on Medea's blame, for stealing Jason's heart away when he left; Hypsipyle's sense in the letter appears to assume Jason's general honorability, but he was in turn a victim of Medea. Chaucer seems inclined to move away from this representation, perhaps because of the proximity of Hypsipyle's and Medea's legend (in the Heroides, they are chapters VI and XII, whereas in Chaucer's poem Medea's follows immediately).