Cooperating with the Corpse Driving Sect was related to a major plan of their White Lotus Sect, and Bai Ling merely hoped to handle the matter smoothly, as this would further her position within the White Lotus Sect.
But some things cannot be achieved merely by wanting them. After Su Xin annihilated the Tang Sect, Bai Ling went directly to Xiangxi Province, assuming Su Xin would surely recover for a while before coming to Xiangxi. However, she never expected that Su Xin would act against the Corpse Driving Sect so soon.
Actually, her earlier words were meant only to scare Yin Tulin; she didn't expect them to become reality.
After pressuring Yin Tulin, Bai Ling turned and left, summoning a female disciple guarding the perimeter from the White Lotus Sect and asked, "Has any message been sent from the Holy Mother?"