User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-24339098-20130609180609/@comment-3146930-20130609190657

Her fatal flaw could be the same as Percy's, Personal Loyalty. I mean she died the first time by sacrificing herself in order to prevent the Gigantes from rising, even if it was only for a short time. However, she didn't really die by protecting others, so it could just be a strong sense of right and wrong. I mean after she was brought back to life, she was still willing to free Thanatos as it was the right thing to do, even if it meant having to return to the Underworld. Going by that, her fatal flaw could be her convictions.