I dont think chakra cast by genjutsu can be deflect by mirror(I know Yata mirror can but not normal mirror). I think that give you the clue
We knew genjutsu was not a simple stare into person(victim) eyes but it also transfering genjutsu chakra emit by the user(caster) into the victim eyes, brain and chakra path way. And the problem here the mirror just projecting the image. The actual/real living person is not inside the mirror.
An Uchiha doesn't need a mirror to set a genjutsu on themself. If i'm not mistaken, Sasuke broke out of a genjutsu by overlapping it with another genjutsu and then breaking out of that one, or something like that. Very confusing.