LAPD Patrolman Samuel L. Walker died during the Influenza Pandemic of 1918. He left behind a wife, Addella, also ill with the flu, and three small children--one newborn. The couple had been married only seven years.
Addella recovered. She had to leave the new home the couple had bought at 526 N. Bonnie Brae (the house still stands) to move back with in with her mother. In March, 1919--a few days after what would have been her 8th wedding anniversary, she joined the LAPD as an officer in the Juvenile Bureau.
Addella was not the first woman on the police force. That honor goes to Alice Stebbins Wells, who in 1910 became the first female police officer in the U.S. with arrest powers, right here in Los Angeles. You can read about Mrs. Wells on the official LAPD site. The second woman was Minnie Barton.
Could not find out anything about Addella at the LAPD site; this picture and information came from the Los Angeles Times of March 15, 1919.