The girl was found with "significant injuries" inside their apartment Tuesday, and she later died at the hospital. Eyewitness News learned the death involved a frying pan, but the nature of the toddler's injuries were not revealed.
Carmen Anita Degregg, 24, was taken into custody shortly after and has been held on $2 million bail.
On Thursday, Degregg was charged with murder and assault on a child causing death. She is expected back in court on Friday.
If convicted as charged, Degregg faces up to 25 years to life in state prison.
A cause and manner of death of the child will be determined by the L.A. County Medical Examiner.
An investigation is ongoing.