@Rignak It might not be an error as such. If her name is spelled with a vocalized つ (tsu), as opposed to a vocalized す (su), then "Kouduki" is a legitimate romanization. There are two romanization systems for Japanese; one of them transliterates づ as "dzu", the other as "du". This is the same principle that gave rise to the "Feeding the Ducks" pool here; the Akizuki-class destroyers can legitimately have their names romanized as Akiduki, Hatsuduki, and Teruduki, thus the semi-visual pun of -duki -> ducky.
tl;dr: "Kouduki" is a legit alternate spelling, even if it's not the default one.