Lady Mi was a younger sister of Liu Bei's associate Mi Zhu who gave her to him as a principal wife after Liu Bei's wife or wives and children had been captured by Lü Bu in 196. Though information on her life are scarce, she is mostly remembered for sacrificing her life in the Romance of the Three Kingdoms at the Battle of Changban to assure that Zhao Yun and the infant Liu Shan are safe from their pursuers.
Lady Mi was from Qu County (朐縣), Donghai Commandery (東海郡), which is present-day Lianyungang, Jiangsu. She had two brothers: Mi Zhu and Mi Fang from the influential and wealthy Mi clan in the Xu Province (present-day northern Jiangsu), who previously served the warlord Tao Qian. After Tao Qian's death, they supported Liu Bei to be the Governor of Xu Province and joined his side. When Lü Bu led his forces to seize Xiapi(下邳; present-day Pizhou, Jiangsu), the capital of Xu Province from Zhang Fei. Mi Zhu sponsored Liu Bei with all of his family wealth and Lady Mi become Liu Bei's first wife during his family absence. Some domestic complications must have followed, for we are told Liu Bei made peace with Lü Bu soon afterwards and his family was returned to him. Lady Mi is never referred again.
Liu Bei's family was captured once more by Lü Bu in 198 to be again returned later and in 200 he was obliged to abandon his dependants to Cao Cao however that group never rejoined him.Rafe de Crespigny suggest that if Lady Mi was still alive, surely she would have been mentioned during those later event hence he believes she must have died sooner in 197.
In the 14th-century historical novel Romance of the Three Kingdoms, during the Battle of Changban, Lady Mi was lost in the midst of the battle and was injured while carrying Liu Bei's infant son Liu Shan with her. Zhao Yun went to search for them and found them beside a well. Zhao urged her to follow him but she refused, not wishing to burden him. After entrusting Liu Shan to Zhao, Lady Mi committed suicide by throwing herself into the well. Zhao knocked down a wall to cover the well to prevent their pursuers from finding her body.
A poem honored her sacrifice with those lines:
The embattled captain had to have his steed;
On foot he could not save the little prince.
Her death preserved the Liu dynastic line:
For bold decision mark this heroine.
Later on, when Guan Yu met Liu Bei after they escaped with Lady Gan and saw that Lady Mi was absent, he asked his brother why he couldn't see his other sister in law. Liu Bei could only recount her heroic sacrifice to save Liu Shan in Dangyang. Guan Yu sighed and reproched him not going with his advice during Cao Cao's hunting expedition at the capital.