Why did the white snake cultivate into a snake fairy?

The name of White Snake is White Snake, which has been practicing at the foot of Qingcheng Mountain in Sichuan for thousands of years. In fact, the White Snake is the reincarnation of the Arctic purple star in the sky. Because she had a snake body with Nu Wa, she was mistaken for a snake demon. Her parents are Nuwa's guardians, Bai Bian and Teng She, which shows the high status of Mrs. White Snake. Fahai can't fuck her. There are many versions of this story. ) Before she was relegated to the immortal class, Master Guanyin said that she would repay 1700 years ago Xu Xian, who begged her, and then become immortal after her death.