When they first introduced her, they called her Yukiko Abe, but then the next few chapters that I read were translated by a different translator, and they translated her name to "Yukiyo Abe". However, Wikia says that the kanji for her name is 由紀子, which would be read as "Yukiko".
So which is it? Yukiyo or Yukiko?
Her full name is Yukiyo Abe.
Japanese Wikipedia listed her name as
アベ ユキヨ（黒髪ポニーテール）
Yukiyo Abe (Black Ponytail)
MyAnimeList also confirms the name as
Yukiyo "500 Year Old One" Abe
As for why the translator seemed to confuse "Yukiyo" with "Yukiko", コ (ko) and ヨ (yo) looks similar, having only 1 stroke difference. In addition of that, Yukiko is a more popular name in Japan than Yukiyo. Note however, her name is never written in kanji, thus there is no official kanji representation of her name.
