Lanling Warrior-Granny Wu Xue's Divination.

Only Zheng Fei knew, but Grandma didn't tell Xuewu that she was the future Zheng Fei, probably because Grandma knew that the soldier Lanling would eventually die, and in order to protect Xuewu from harm, Grandma didn't tell her that she was the one who would eventually be with the soldier Lanling. Snow dance was given the surname Zheng by the grandmother of the Lanling warrior, hence the name.