Bora Kim was spotted by rescuers and airlifted out of the canyon at about 7:35 a.m.
Kim, who is from Arcadia, was reported missing by her parents, who last saw her when she was dropped off at a bus stop headed for school at about 8 a.m. Thursday.
Later in the day, Kim sent suicidal messages to an ex-boyfriend, who recently broke up with her, according to Arcadia police.
At about 6 p.m., a friend received a call from Kim saying she was lost in the mountains. Friends told authorities that Kim often hikes in the Eaton Canyon area, and the search commenced.
Crews scoured the Altadena and Sierra Madre areas overnight and into Friday morning.
Kim has been taken to an area hospital. There was no word on her condition, but she was seen moving on the ground before her rescue.