Amanda Sorenson, 21, of Apple Valley was present and in custody Thursday inside the Victorville Superior Court for her arraignment, according to court records.
Sorenson has been charged with murder and assault on a child causing death. If convicted, she could receive a prison term of 25 years to life.
She is scheduled to be back in court on Jan. 17, according to court records.
Deputies were called to the 20000 block of Cayuga Road on Sunday night when they found 2-year-old Joileen suffering from a seizure after ingesting the powder, authorities said.
The girl was taken to the hospital where she was pronounced dead. An autopsy is scheduled to be performed.
Sorensen is the girlfriend of the toddler's father, officials said. The father's name wasn't released.