I have my assumptions. After all... your hair, Seteth's, Rhea's, and the professor's after the incident... they're all similar. I may not be a religious woman, but I do know there is some sort of blood connection. Otherwise they would not have gone to such great lengths to take blood from you.

[After all they had plenty of children to experiment on over the years. There had to be something special about Flayn's blood in order for them to risk so much.

Edelgard is perhaps more willing to accept "child of the goddess" now than before, but even back then "not entirely human" was at the top of the list.]