How did Mu Xiaodie and Yang Jian know each other?

Mu Xiaodie and Yang Jian met each other during an encounter in the plot of the second part of the God-Sealing List of Heroes. At that time, Yang Jian was imprisoned in Zhaoge City of the Shang Dynasty, and Mu Xiaodie was a princess of the Shang Dynasty. She rescued Yang Jian through some means and helped him escape Zhaoge City. In the process of escaping, the two gradually developed feelings for each other and became each other's partners.