Mariam Filihia was sentenced at the High Court in Auckland in October to a minimum of 17 years in prison for killing Terepo Taura-Griffiths, known as Popo.
During the trial the Crown argued the one-year-old died after Filihia struck his head against a hard surface in November 2011.
But Filihia's lawyer said there was no evidence his client caused that injury.
Filihia's new lawyer Lorraine Smith says she won't comment comment on the grounds of the appeal at this stage.
