"They found that she was gravely ill and was covered in human waste and had not been cared for in quite some time," Smith said.
Gladstein was taken to West Hills Hospital, where she was pronounced dead at 11 p.m., Smith said.
The victim's daughter, Belinda Feldman, 54, was arrested on suspicion of elder abuse and abuse of a dependent adult, with other charges possible, Smith said.
Neighbors told the TV station that Feldman has a history of mental illness and sometimes stops taking her medication.
She was jailed in lieu of $50,000 bail.