The 19-year-old, of Packett Street, Fenton in Stoke-on-Trent, is due to appear before magistrates at North Staffordshire Justice Centre this morning.
The young mother’s 22-year-old partner, named locally as Paul Hogan, was also arrested – but he has since been released on bail pending further inquiries.
Forensic officers were seen combing the terraced home where Cody-Anne and her partner lived, after police smashed their way into the house at 10am on Monday.
Staffordshire Police said a post-mortem examination showed no clear cause of death so further investigations would take place.
The toddler’s great-grandmother, Mary Garwood, broke down in tears as she described Macy as a ‘gorgeous’ little girl who was always smiling.
She said: ‘We just can’t believe it. We still don’t know what happened. Her mum just phoned me up and said Macy’s dead and Cody-Anne’s been arrested.
‘Macy was such a gorgeous child. We’re devastated.’
Detective Inspector Dan Ison said: ‘I urge members of the public not to comment or speculate about this on social media and to remember that a little girl has tragically lost her life.
‘Our thoughts are with the little girl’s family at this time. ‘This is a very distressing incident and we are doing all we can to support those affected.’