Authorities say she left the infant, along with his 2-year-old brother, inside a hot car.
Prosecutors allege last month, 20-year-old Maya Hernandez left the boys in the car for two and a half hours while she had a cosmetic procedure done and never went to check on them.
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1-year-old Amillio Gutierrez died, but his 2-year-old brother survived.
Hernandez is now being held on more than $1 million bond and is due back in court next week for arraignment.