There are thousands of them: foreign women who married Daesh (aka IS, ISIL or ISIS) men and who are now sitting in refugee camps, in many cases with their children. Some are alleged to have attacked other refugees whose behaviour does not conform to Daesh norms, and even to have set firs to those people’s tents.

Mother and Child in a Kurdish-run Camp
Their home countries are reluctant to take them back, for understandable reasons. It’s hard to believe the claims that they were too young to know what they were getting into, or were taken in by the propaganda about the creation of a perfect Islamic state and somehow missed the bits about murder, torture, rape and slavery.
The case of Shamima Begum has hit the headlines in the UK, whence she fled at the age of 15 to join Daesh. Her Dutch husband survived the fighting and has renounced Daesh. Shamima wants to go home with her baby. The UK doesn’t want either of them. It’s a similar story with Australia Zehra Duman. An estimated 9,000 are nationals of the Russian Federation (mainly Chechnya) and other former Soviet Republics.
My view is pretty simple. These people, however wicked, deluded or gullible they may have been, are citizens of countries which have laws, institutions and financial resources far beyond those of the Kurds and others who are holding them. It’s our responsibility to receive them back, subject the adults to due legal process, and care for the children in such a way that they will grow up sane, productive and law-abiding. This will not be cheap, but it will surely be cheaper than letting stateless extremists and their hapless offspring roam the world working mischief.
I just checked, and Australia still has a law dealing with treason. It is contained in Chapter 5 of the Criminal Code. The penalty for intentionally assisting, by any means whatever, another country or organisation [my emphasis] that is engaged in hostilities against the Australian Defence Force is life imprisonment.
The law is specifically framed to include terrorist organisations. One would hope that the phrase “by any means whatever” is broad enough to encompass making one’s way into a war zone to marry an enemy combatant and bear his children, who will be educated in extremism and brought up to be Daesh’s foot soldiers – and martyrs if they’re lucky.