Anyone who doesn't even consider an imposter in a world in which cosmetic magic has been confirmed to be widely practiced enough that changing your face is illegal is too stupid to live. Like, wow. "I saw this person committing a crime!" While she wasn't there. And you don't think maybe it's an imposter simply using magic for a disguise?
Asian writers especially have a tendency to make stories/arcs/whatever that completely ignore their own world-building as if the characters don't exist in the world the writer made, resulting in the capabilities of that world not being taken into account. This is an example of that.