She need to protect him until she can take out the evil bone. If TTJ die before that, the demon god will born.
what @Kaseh Esmiralda said, she has to keep him alive until she finds a way to find and destroy the evil bone he is already on the path to being evil (forgot the exact episode where it's shown explicitly to viewers)
and what the other person said
:D this drama
as her name is bingchang not bingcheng
it was stated in the eps that the dragon was ming ye, he created the dream thing which the characters are put into
xiao se and sikong qianluo
fairy rui and tang lian
li hanyi and zhao yuzhen
lei wujie and ye ruoyi
https://www.youtube.com/playlist?list=PLHal96yJvQA-auvL19pbPaBbn-RoiJaQ6
he is already on the path to being evil (forgot the exact episode where it's shown explicitly to viewers)