A glance at the life of Aqsa Mahmood, a young Scottish Muslim woman who abandoned a comfortable middle-class background to join the Islamic State in Iraq and the Levant (ISIL) in Syria, reveals an almost classic case of conversion to extremism.

To friends and family, she was studious and kind-natured, a devout but westernised student with the same everyday concerns and interests as other Asian girls in her mixed circle of acquaintances.

Gradually, the privately educated daughter of a Pakistani businessman withdrew into a world dominated by hours of internet research of Islam and jihad.

From listening to Coldplay, reading Harry Potter, sharing her father’s passion for cricket and aspiring to a career in pharmacy, she became obsessed by the cause of Islamist extremism.

And 10 months ago, she left Britain for Syria to embrace what the British prime minister, David Cameron, this week called a “poisonous ideology”, relying on the most brutal forms of terrorism “to force people to accept a warped world view and to live in a medieval state”.

She has since married a Syrian fighter and, on the evidence of her social media messages, rejects all the trappings of the world she left behind.

Her role in Syria appears to be largely supportive, cooking, cleaning and child care. But her prolific tweeting betrays the hardened outlook she has developed.

Hostile references to “kuffar”, or non-believers, suggest she regards even the non-Muslims she grew up with as worthless enemies.

There is no indication that Mahmood has taken part in combat or terrorist operations.

But she tweeted with warm approval about witnessing the executions of two captured Syrian soldiers and leaves no doubt about her ringing endorsement of ISIL violence.

Mahmood appears to be precisely the sort of convert to extremism that Mr Cameron had in mind on Monday when he announced plans to tackle both the outward flow of recruits to militant groups, and their return as possible security threats to the UK.

Among other young female recruits in recent months have been Salma and Zahra Halane, 16-year-old twins from Manchester, also promising students, who disappeared from home in May.

They telephoned their parents from Syria to tell them they were “not coming back”.

Among a stream of tweets bearing witness to her radicalisation, Mahmood encourages Islamist attacks in western countries.

She praises last year’s Boston marathon bombing, a mass shooting that left 13 people dead at the Fort Hood United States military base in Texas in 2009 and the murder of Lee Rigby, a British soldier stabbed and hacked to death by two Islamist extremists in a south London street near the Woolwich barracks last year.

Using the name Umm Layth, she tweeted in June: “Follow the example of your Brothers from Woolwich, Texas and Boston etc. Have no fear as Allah swt [Subhanahu Wa Ta’Ala or Glorified and Exalted be He] is always with the Believers.”

Openly advocating atrocities in the US, the UK, France and elsewhere, she wrote in successive messages: “Jihad is not limited to Shaam [Syria], Khurasan, East Africa, Yemen, etc. It is a worldwide battle against Kufr. If you cannot make it to the battlefield then bring the battlefield to yourself.”

Mahmood’s Twitter account profile – now deactivated – carries a picture of ISIL’s black flag. She makes no obvious attempt to rationalise the organisation’s brutality.

Friends in Scotland are said to be horrified that this intelligent and previously warm young woman could now be happily associated with a movement known for its savagery, from ISIL fighters’ self-proclaimed genocide against Christians and Yazidis in northern Iraq to the massacre of captured Syrian soldiers or beheading of civilian hostages.

But she rails against whoever leaked information that led to media reports of her case.

In a two-part message sent last month, she wrote: “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].”

In a perhaps more vulnerable moment, at her Tumblr blog in May, Mahmood showed lingering sentimentality when she reproduced another writer’s words.

“I miss my mother. I want this to be a reminder to all of you, to recognise the worth and value of your mother, because once you lose her, nothing will be the same again.”

And she retweeted a message offering a militant’s apologies to his mother: “I know I upset you by leaving for jihad.”

Mahmood’s parents have declined to comment but are described in British media reports as devastated by their daughter’s disappearance.

A police statement said: “A 19-year-old woman from Scotland was reported missing to Police Scotland by her family in November 2013. Inquiries are continuing in relation to her whereabouts and we are supporting her family.”

Police are satisfied she is in a conflict zone.

Mahmood is now 20. Her father developed successful businesses after emigrating from Pakistan and his daughter was sent to one of Glasgow’s top private schools, Craigholme, where fees are £3,720 (Dh22,514) a year.

A former school friend told the Daily Mail newspaper Mahmood loved make-up, clothes and teenage gossip.

“She wasn’t different,” the friend said. “She got on with everybody. As soon as she decided to do something she would never change her mind. I guess that was something that was amazing about her, but also one of her downfalls.”

Mahmood was in her fifth year at her independent school when her interest in Islam noticeably deepened. She took to wearing a hijab, and later abayas, bought religious books and avidly studied aspects of Islam.

Her academic studies appear to have suffered and her higher examination results were disappointing.

She switched to Shawlands Academy, a mixed state school in Glagsow, where she was also regarded, according to another friend quoted by the newspaper, as “just the usual Asian Muslim girl”, bright with many friends and able to communicate with anyone.

Mahmood gained admission to Glasgow’s Caledonian University for a course she left last year to travel to Syria.

It is clear she became steadily interested in politics. At least one friend has spoken of her expressing a desire to help fight the Syrian regime of Bashar Al Assad.

But as recently as two years ago, answering questions on the ask.fm social network, she was still outwardly a cheerful, open-minded teenager.

To one reader who praised her “pretty” hijab, she replied: “Thank you! :) it’s actually so simple, takes like a few minutes.”

In other answers, she spoke of intending to complete her pharmacy studies, nominated her father as the “best cricketer” and described herself as a “true Scot” who preferred the kilted Craigholme school uniform to that of Shawlands.

She dealt briskly with a reader who posted a salacious message, saying: “This reminds me why I tried staying away from ask.fm.”

There was, in those online comments, no indication of what lay ahead.

As media interest in Mahmood grew this week, belated action was taken to block her Twitter activity.

A Police Scotland spokeswoman said she could not say whether any request had been made to Twitter. The company did not respond to questions.

But it is known that British police forces regularly seek the cooperation of social media providers when there is suspicion of criminal activity, which in this case would include incitement to violence.

It is still possible, however, to read many messages from Muslims condemning her actions.

“You’re an absolute embarrassment,” wrote another young Glaswegian, Fahdi Bari. “You don’t know the definition of Islam. Disgusting.”

newsdesk@thenational.ae