The mirror image spell description says
Each time a creature targets you with an attack during the spell's duration, roll a d20 to determine whether the attack instead targets one of your duplicates.
It does not prohibit targeting the illusory duplicate themselves, especially for a non-hostile effect.
Two examples from features with a similar effect are:
The Goblin Boss (MM, p. 166) has the Redirect Attack reaction:
When a creature the goblin can see targets it with an attack, the goblin chooses another goblin within 5 feet of it. The two goblins swap places, and the chosen goblin becomes the target instead.
The Way of the Drunken Master monk's 6th-level Tipsy Sway feature also grants a benefit named Redirect Attack (XGtE, p. 34):
When a creature misses you with a melee attack roll, you can spend 1 ki point as a reaction to cause that attack to hit one creature of your choice, other than the attacker, that you can see within 5 feet of you.
Note that those are just examples. The point of the question is whether the duplicates can be targeted by such attacks or effects, either knowingly or unknowingly it's a duplicate.
Also note that most non-attack effects simply bypass mirror image by directly affecting the mirror image user. However, for other effects, this question asks about the more fundamental principle: whether the duplicates are actually targetable or not.
A point of consideration might be whether an effect that specifies a creature as its target is unable to target mirror image's duplicate - or whether any effect is simply unable to target the duplicate, and could only target the original target.