ye i hope she isn't really her real mother but i doubt it. usually adopted parents in manga are always more caring especially in something like a shoujo manga.
yup, there's some twisted idea in my mind:
1. kyoko is her dead sister child, and her sister had taken saena's boyfriend or worst fiancee maybe.
2. Kyoko is her dead sister whom she hates so much because they parent always compare them.
many possibility (〜 ̄△ ̄)〜
note: pardon me, english isn't my first language.
Geh!!!In each of the cases it's not the poor childs fault to be treated that way!Even if shes not her mother she should have at least told her that instead of ignoring her and criticize her since she was young.So in my book in any case shes a coldhearted bitch and no matter what happens and no matter the reason Yoshiki-sensei is gonna give later i dont think i ll change that opinion, cause Kyoko was suffering for the tenderest of her years..
what if, kyoko really isn't her child, like her sister's child or something and kyoko's parent die in accident, that's why she despise her so much because she thinks kyoko is a burden?
just my theory (〜 ̄△ ̄)〜