Board Thread:Speculation House/@comment-27394360-20151214040010/@comment-86.14.243.230-20151214193732

One popular theory goes that Emerald is the perception - alterer while Neo actually has a semblance relative to time distortion; This explains how she managed to get herself and Roman away from team RWBY after the battle on the highway, and when she teleports away from Raven on the train. She can slow down her own timeline; enabling herself to move while others can't see her (Something she can obviously grant other people i.e Roman, possibly through touch). The After images she's known for are a secondary effect of the time distortion - She can leave a mirage whenever she activates her semblance.

This is the glass wall that Yang punched last season, and is also demonstrated right before she fights Yang on the train, leaving an illusiojn of herself that Yang tries to attack which drops the moment Yang makes contact with it; Where it appears Neo took the attack she actually evaded it and jabbed Yang with her umbrella. When she teleports away from Raven, the result is visibally instantaneous, as there is no need for her to leave an afterimage as she doesn't need to distract; only escape.