I've read from the beginning and yeah I am sure that's the second or third time that ML is jumping through time.
First big difference is that the father is dead which made Uri the new Duke and FL became the knight of the household.
Second big difference is her behavior with Aquilla, really loving, no hate but I doubt she would ever dump her knight role that's why I think there is a timeline where FL became the duchess which would explain why ML can't stop to call her like that.
But for whatever reason she still die in the end so it seems for now, she should avoid to become a knigh or either duchess as long as her fahter is alive.
Anyway, this guy life is sad, he saw her already die once and probably twice...