Originally Posted by
OnesFleetingGlory
Probably due to her portrayal in later years, with Septem likely to be the main cause. Another reason would be that her character can be... pretty overwhelming for people in general. I like her too, but building a relationship with someone like her needs a lot of commitment for it to work, since she believes she deserves their attention more than anyone else.
Hakuno is basically a blank slate at the beginning of Extra, and Nero sympathizes with them and treat them as someone who needs her care. And slowly, she reveals her actual characters bit by bit until both of them come to understanding, which is probably why her route worked imo. Were it any other person, she would act haughty from the start, which might be unnerving.