Police said she stripped about midnight Wednesday, hauled down the flag and then wrapped herself in it, brandishing a lighter and fire extinguisher.
Then, officers said, she began throwing construction glue from the building, listed as having 12 floors. Several vehicles were damaged.
Officers say she appeared to be in a mental health crisis and may have been taking stimulant drugs.
Arson investigators said they didn't know whether she was linked to a rooftop fire at the nearby 15-story Yeon Building that broke out about the same time.
Firefighters contained the fire in about 20 minutes.