Valentina Lore was last seen on March 3 near the 900 block of N. Broadway Street, authorities said.
She is described as being 5 feet tall and weighing about 110 pounds. She has shoulder-length blonde hair and brown eyes.
Lore suffers from Crohn's disease and relatives are concerned for her safety, according to the LAPD's Missing Persons Unit.
If you have any information, you are urged to contact police. Anyone wishing to remain anonymous should call the LA Regional Crime Stoppers at 1-800-222-TIPS (800-222-8477).