For Javornik, World War I started with the battles around Šabac, during the Battle of Cer, in which her uncle, Captain Martin Javornik, was killed.
The war then took her to Belgrade, where she participated in the defense of the city.
Together with the rest of the Serbian army, she retreated over the mountains of Montenegro and Albania and witnessed the death of many on the islands of Corfu and Vido.
After a period of recuperation, she came to the Salonika front and participated in the Battle of Kaymakchalan, fought between 12 and 30 September 1916.
After the fall of Kaymakchalan, the breach of the Salonika front and the liberation of Bitola, she received her most valuable medal, the Karadjordje's Star with Swords.