Huh... 🤨 there seems to be an inconsistency with Byakuren's getup now that I look at it. A lot of artists tend to make the skirt flow way past her knees to make her seem more imposing. But if we refer to just by how she looks in UFO, even if we account for the fact that it's flared out there, the skirt is at best just past her knees.
It's a short dress.