The 27-year-old actress was placed under the 5150 hold last month after being arrested for starting a small fire outside a stranger's home and a judge has denied her motion to be released and ruled she must remain at the facility in Los Angeles until August 9, according to RadarOnline.
The decision insisted Amanda is not stable on her medication and needs to remain under medical supervision.
The 'Easy A' star, who retired from acting to focus on carving out a career in music, has been displaying signs that she is suffering from mental illness since she was taken into police custody.
An insider previously revealed that Amanda's parents, Lynn and Rick, believe she is a danger to herself and are hoping to secure a conservatorship that would give them legal control over the actress until she gets her life back on track.
Amanda was arrested and admitted to hospital after using a canister of gasoline to light a fire on woman's driveway in Thousand Oaks, California.
She accidentally soaked her Pomeranian puppy in gasoline and surveillance video showed her rushing into a nearby liquor store to wash the pet.
The dog is now in the care of her parents.