Saw this in the news portals the other day but since no english translations, heh! have to wait. She was that deranged girl in Boys over Flower.
Credits to ystarchannel1 + (English translation) firstname.lastname@example.org
Talks about Lee Siyoung has been a fan of the original manga since the beginning, and wanted to portray a different charm to her korean version character, so she decided to take on the role.
It will be her 2nd time working with HJ. And her role is Yoon Hae-ra (윤헤라), rival of Ha-ni.