It honestly depends on route. How exactly it works out for the various characters depends on which route you take through the game. On ONE of the four routes she goes absolutely bonkers and becomes that thing you see in the last panel. On one other of the routes everything works out extremely well for her. On the other two… mixed bag.

In all 4 routes she could totally have handled it a lot better, but if you've seen all four paths it's actually easy to take the stance 'somebody needed to do something dramatic, even if it was just fucking up on a grand scale, so that the chance for SOMEBODY to fix things would become available'.

well being fair, Dimitri is wrong about that, at least regarding the whole Duscur thing

Of course, you also have the other side of the coin, people who played first BL and think Edelgard is rotten to the core (When she's just misinformed and stubborn as hell)