The two became a 'poster girl' for Isis, also known as Islamic State, appearing on social media websites in images showing them carrying Kalashnikovs and surrounded by armed men.
But by October that year there were reports quoting friends of the two women saying Ms Kesinovic had been sickened by the killings she witnessed and wanted to come home.
According to local Austrian media Ms Kesinovic was murdered by the group as she tried to flee the Isis stronghold of Raqqa.
One report quotes an "insider", an unnamed Tunisian woman who reportedly also travelled to Syria to join Isis lived with the two girls while in Raqqa, but later returned home.
The Austrian foreign and interiror ministries declined to confirm the reports.
In pictures: Russian air strikes in Syria
Show all 19
A report last year by David Scharia, a UN counter-terrorism expert, that a 15-year-old girl of Bosnian origin from Austria who had joined Isis had "disappeared" is now thought to refer to Ms Kesinovic.
Mr Scharia said: "We received information just recently about two 15-year-old girls, of Bosnian origin, who left Austria, where they had been living in recent years ...one was killed in the fighting in Syria, the other has disappeared."
Both Ms Kesinovic and Ms Selimovic were children of Bosnian refugees who fled to Austria in the nineties to escape the war in their country.
In April 2014 the two travelled, via Turkey, to Syria where it is believed they both married Jihadists.
Syria: Russian jets pound ISIS oil refinery in Syria
The Austrian authorities have accused a Vienna-based Bosnian Islamic preacher known as Abu Tejda - named as Mirsad O under Austrian privacy laws - of recruiting the woman.
He denies the accusation.
Subscribe to Independent Premium to bookmark this article
Want to bookmark your favourite articles and stories to read or reference later? Start your Independent Premium subscription today.
