She stayed not only to save Xiao Wuyan but also to save Chu Liang.
Although it was Chu Liang who had put her into Sky-north Prison with great effort, she now meant to follow a path of good and did not wish her sister to continue as an enemy of the Righteous Path. Moreover, she clearly saw the plight the Human Clan faced—the Human Clan was in a state of disarray, and Chu Liang was one of their hopes. She decided she could no longer contribute to tyranny; killing Chu Liang at this time was absolutely unacceptable.
Thus, after parting with the Heavenly Master, she searched atop Seven Kings Ridge, planning to rescue both Chu Liang and her sister.
However, she hadn't gone far when she witnessed the Black Gold Crow launching a deadly attack on "Chu Liang."
According to Xiao Wuyin, there were three Chu Liangs on Seven Kings Ridge at present: the real Chu Liang, her sister, and the Fox Demon King, Cai Yi.