Ming Feichuan, a female doctor, personally killed Mrs Xu.
In the original work, because Mrs. Xu has the symptoms of Li Xia, but she didn't tell the heroine, the sum of the symptoms of night sweats and chills led the heroine to mistakenly think that Mrs. Xu is yang deficiency, so she gave Mrs. Xu licorice and Jiang Shui. And Dr. Wan did give Dr. Xu a pulse-taking diagnosis of yin deficiency. So one raises yin and the other helps yang, which finally led to the accidental death of Mrs. Xu. So it was because Mrs. Xu didn't explain her illness clearly and took contradictory drugs before and after, which led to her death.