Thanks for your constructive comment, it helped me think about the topic from a different perspective. I can kind of see what you're saying. And I agree, change can be good sometimes.
I don't follow what modern nobles/aristocrats/celebrities/upper-class/rich do so I can't say I'm experienced in their current trends. I also can't say anything objectively since this topic is largely subjective.
So what I'm about to say is pretty biased. When I think undercut, I think of Miley Cyrus or
, people who try to be (a lack of a better word) 'edgy'. When I think of nobility, I think of those old fancy European parties where the women wore a lot of powder and had big dresses. I don't think Fiora would get that 'edgy' haircut as it would risk hurting her noble family public image. She seems too elegant and self-restrained to do that as well. Fact is, the haircut breaks away from the 'normal' or traditional haircuts today, so its return was intended to make a statement or to 'stand-out'. Of course, maybe Fiora decided it was time for change.
Admittedly though, after looking at some of the images of undercuts from that Bioluminescence linked, it does look really cute on some women...