Although Zeng Yanli was stupid, she wasn't a woman who was too stupid.
When she found out that she had been set up by Wen Yujing, she knew that Wen Yujing did not want her to marry Jiang Zhenye.
Therefore, those words that she had said to her before, that she liked her as his daughter-in-law, were only if she married Jiang Zhennan, not Jiang Zhenye.
However, she was betrothed to Jiang Zhenye by the Emperor, and Wen Yujing immediately turned against her.
Seeing that the marriage was getting closer and there was no way to break off the engagement, she thought of such a vicious and poisonous plan to ruin her innocence and prevent her from marrying Jiang Zhenye.
Even though she no longer had any innocence to speak of.
In the end, the truth was revealed.
Her innocence had been destroyed by her future mother-in-law, so the Emperor had no reason to take back the decree.