Why did Yang's grandmother die?

Divination cannot be used easily. Divination once every ten years will make grandma lose her eyes. Grandma kept Xuewu for the last time, but Xuewu called her to save Grandpa Four. Grandma left a plan to help them through this difficulty. I guess that's why grandma died, because her secret can't be revealed.

Although Yang's grandmother is blind, she is a wizard's grandmother and knows divination. When she was very young, she not only saw the internal and external troubles of the Northern Zhou Dynasty and the Northern Qi Dynasty, but also saw the future situation of the world.