That is completely ridiculous.

You understand that, don't you?

Edelgard was a child - she did not have the power to cause Duscur. Nor did her father as he had been crippled by his own nobles a few years before. It is akin to blaming an armless man for shooting you with an arrow. It is entirely possible Adrestia is responsible for Duscur somehow, but it was not Edelgard's doing.