The rules, in this case are pretty clear. The spell never mentions mirrors or reflections, it “summons illusory duplicates." Spell names aren’t indicative of their mechanical effect. See Chill Touch.
There’s also vampire wizard statblock that has Mirror Image on its spell list.
It would be funny if the spell just failed though.
I don’t I can make a good case for “looking in a mirror” to use the “attack” rules. If it’s an attack you’d have to make an attack roll (if you’re not making an attack roll, it’s not an attack.)
Likely, if there was a d20 roll involved, it’d be a perception check.