Before the Demon Flower died, she made a promise. "Bai Wuchen, I don't want to put you in a dilemma this incarnation, so I choose to die under your sword. The next incarnation, I won't be a demon again. I'll be a mortal. I'll be together with you. You can't betray me. If you betray me, I'll become a demon again and I certainly will pay you back."
It was the Demon Flower's ability. Once she made a promise, it could become reality.
At this last moment, Bai Wuchen was touched. Although he still disliked her, he felt guilty because she died for him. He also promised that he would protect her throughout their life if she became a mortal in the next incarnation. Therefore, the Demon Flower became a mortal named Hua Lingge in the next incarnation. However, she lived a terrible life.