She was a member of Nili (a ring of spies that worked for the British during World War I). She is sometimes called "the heroine of Nili".
After seeing thousands of Armenians being killed and tortured while she was traveling from Istanbul to Haifa, anything that reminded her of Armenians would lead her into a fit of hysteria. She started up Nili with her two brothers and a friend to help the British during World War I.
In September 1917 the Ottomans caught one of her carrier pigeons which they then worked out (decrypted) and found out where she was. After arresting lots of people, the Ottomans tortured Sarah Aaronsohn for four days before she managed to find a gun to shoot herself with. In her last written letter she said that she hopes her activities with Nili would help bring the Jews a home country.