Aqsa Mahmood, 20, left her Glasgow home in November and fled to Syria where she married a fighter with the terrorist group Islamic State in Iraq and the Levant (IS).
On Wednesday, her family made a desperate plea for her to return home the day after footage emerged of a second American journalist, Steven Sotloff, being beheaded by extremists in the desert, and as the British Government hardened its stance against the brutal Islamic State amid domestic terror warnings.
Khalida Mahmood and Muzaffar Mahmood said they were horrified to learn their daughter had become radicalised.
They spoke after comments attributed to their daughter on Twitter called on people in Britain to repeat terrorist atrocities seen in Woolwich and the US.
A Twitter account under the name Umm Layth, believed to be Ms Mahmood, was used to promote terrorism. The account, which carries a picture of the black flag of the terrorist group IS, has been deleted, but not before concerns were expressed the that the family's security was now compromised.
Tweets seen by The Herald, dated August 26, indicate concern over leaked information that led to recent media reports of Ms Mahmood's case.
"By the Lord of the Kabah, know that whoever it is that gave away my details and initially have affected my families security - I have an appointment with you on the Siraat (a bridge over hell)," said one tweet. Another added: "Read up on how many people reverted to Islam after 9/11. You can plot and plan but you will never extinguish the Light of Islam." A separate tweet said: "And a message to the Kuffar [non-believers], thank you. If anything you make it easier on us to spread the Dawar [the message of Islam] Keep printing those papers :)."
A tweet in June said: "Jihad is not limited to Shaam [Syria], Khurasan, East Africa, Yemen, etc. It is a worldwide battle against Kufr [the action of showing ungratefulness to Allah and disbelief]. If you cannot make it to the battlefield then bring the battlefield to yourself."
It is understood that Police Scotland liaison officers are assisting the family while they make inquiries about her whereabouts.
A spokesman for the family said: "The family just want her back safe." The family had been in contact with their daughter through social media but contact ceased on Tuesday after details of her involvement with the Islamic State was revealed. Ms Mahmood, a former pupil of Craigholme Secondary School, one of the city's most exclusive girls' schools, had not been seen by her parents since November last year.