Nicola Long, 42, is being held in custody in connection with the death of Jake Long on December 19, 2014.
She also faces a count of causing or allowing a child to suffer serious physical harm.
The woman, from Portsmouth, Hampshire, is due to appear before the city’s Magistrates’ Court on Tuesday.
Hampshire police have also charged 43-year-old Jason Brown, of the same address, with causing or allowing a child to suffer serious physical harm and he will appear alongside Long in court tomorrow.