Didn't Cheng marry the emperor in the novel version of Master Punishment? How did she become Meng's daughter-in-law again? Tell me what the hell happened.

Because Xiao Wei and the emperor's child miscarried, the emperor knew who did it, but he left without pursuing it. Xiao Wei lost her child, and she lost the capital to compete in the harem. Besides, she was tired of intrigue in the palace. While the emperor was obsessed with alchemy, she begged the emperor to let her go out of the palace. After Xiao Wei left the palace, she always planned never to return to the palace. Meng, whom she always liked, came again. After a premeditated accident, she played dumb and left a step for the emperor to free him. Finally, the emperor naturally ignored it.