She's just dumb like the average MC in these kind of story... Seriously, their goal from the beginning is to change their future ending and they work toward that by changing their actions and the actions of those around them from what it was supposed to be and yet still are surprised each time the story is different from their memory.
changed story since she married the duke at the beggining... 100 chapters later *omg the story has changed ???? *suprised pikachu face*
They aren't still married, just engaged
What??? But she knew she has changed future before ??? Does she has amnesia or is she dumb ? ._.