Anastasia didn't do anything wrong in the beginning of the story, it all happened because of the deal she made with that heartless count. The marriage was honestly the catalyst, since Theodore despised the count's family and the emperor(?) for the tragedy on his family. If Theodore didn't base their relationship with his blind hatred, then they would have talked it out. Or even prevented the drastic events and changes that occured in their relationship in the progress. And now, the spoilers mentioned it being a very pitiful ending. Even mentioning the downfall of their close relationships due to their toxic situation, that no one could alleviate on time...
If You Wish for My Despair