The public broadcaster RTV Slovenija hailed it as a historic achievement for Strahovnik and its radio station Radio Slovenija at the Rostrum since it was first held in 1954.
The International Rostrum of Composers is an annual forum organised by the International Music Council.
It offers broadcasting representatives the opportunity to exchange and publicise pieces of contemporary classical music.
This year, representatives of 27 radio stations found Prana the most convincing piece of the 66th Rostrum, RTV Slovenija said in a release on Monday.
While composing Prana, Strahovnik, 33, worked closely with the Symphony Orchestra to experiment with new sound techniques.
The piece is written for a full-size orchestra and for soloists, who are seated around the concert hall to produce a "surround sound effect".
As the composer said in the release, the orchestra was eager to experiment with new techniques and use materials such as styrofoam on the piano and harp.
She had been inspired to write it by the idea of recreating the atmosphere of attraction between two different poles and of being caught in it.
The composer understands prana as universal energy which circulates in the body and around it.
This is not the first good achievement at the Rostrum for Slovenia, however.
Four years ago, Matej Bonin won in the under 30 category, which was this year won by When, a piece by Latvia's Jakops Jančeviskis, while Slovenian composers also did well before, including Vito Žuraj, who came second in 2012.