Angela Vickrey, also known as Angela Hanna, entered the plea Monday in Kern County court. Charges of assault on a child and second-degree murder were dismissed.
Trinity Hanna died in January after Vickrey rushed her to Bakersfield's San Joaquin Community Hospital. Medical staff found suspicious injuries and couldn't save the child's life.
The mother's live-in boyfriend was arrested on murder, torture and child abuse charges. Eric Foster, who also goes by the last name of Luna, is accused of injuring Trinity.
Kern County Sheriff's investigators said the mother didn't report the abuse her child had endured.
Court documents state Foster admitted to investigators that he physically abused the child on at least three occasions.
Foster has a preliminary court hearing later this month. The mother is scheduled for sentencing in November.