Mizuki was a bit surprised by Viper’s reaction and when later she proved to be a he she was mildly annoyed that she hadn’t noticed his quirk in action and the revelation that he could copy her quirk made her even more wary of him. She couldn’t allow such things and as a result she made up her mind to randomly cast an alternate self while obscuring her own presence sure that the copycat quirk couldn’t copy the quirk of an illusion which was less intensive energywize than her attack phase.

[b]”Speculation is the anchor of action”[/b] she hears in her memory of her training by the “Sisterhood of Steel” so she stops speculating and decides to try phase imaging later when in the company of the odd boy.

She doesn't stop listening or observing what goes on around her collecting as much data as she can on the others who she knows she will eventually be forced to compete directly against. She doesn't have anything against any of her school mates but in competition she knows she must be ruthless and efficient if she is to rise to the top. Also every word and reaction of the others she knows will give her hints of their fears and dreams and as an illusionist the best paths to take to gain the desired reaction.