Under Zeke's malicious gaze, Sakai Nayumi trembled in fear that she hadn't experienced in her entire life. If only she had known how evil this guy can be in the first place, then she wouldn't have to agree to Yuna's ridiculous plan in the first place.
She was only driven by hate and envy towards that peasant girl that made Nayumi agree with her plans without knowing the consequences behind it.
Nayumi didn't really mean harm to Sakura, all Nayumi wanted was to separate her and Ken for good so that she can have her chance to be with him, just like Rin had promised to her.
But seeing her current situation right now, Nayumi immediately recognized that this must be karma's response for what she almost did to that peasant girl earlier in the bar. Karma indeed is a b*tch huh?
As Zeke was taking a few slow steps towards her, Nayumi also is taking a few steps backwards and constantly looks behind while also finding an opportunity to run from here.