Barbara Ann Bawarsky had custody of the boy. An autopsy listed asphyxiation as the cause of death.
She pleaded guilty Monday to murder in what had been a capital murder investigation.
Bawarsky has agreed to testify against her then-boyfriend, Daniel James Gray, who still faces a capital murder charge over the death and remains in custody.
Gray, 52, is also charged with possession of chemicals with intent to manufacture a controlled substance, endangering a child and possession of a controlled substance.