The 18-year-old, who is believed to be living in the ISIS stronghold of Raqqa, north-east Syria, also hit out at the Prime Minister's plans to prevent British jihadis from re-entering the country.She claimed she would not care if she was stripped of her UK citizenship, describing the notion as 'quite laughable'.It comes amid concerns that a growing number of young women are leaving their families in Britain to join the jihadi cause in Syria.Taking to Twitter, the girl wrote: 'In sha Allah [God willing] a day will come when David Camerons head will be on a spike as he continues to wage war on the awilya [protectors] of Allah... and strike terror in the hearts of the kuffar.'She added: 'I really do not understand why Britain is threatening to remove our citizenship like we care lool its actually quiet laughable (sic).'   Although the girl, who uses the handle @UmmKhattab_, has posted photos to the social networking site showing her wearing a niqab with a gun slung over her shoulder, she is yet to reveal her identity.In recent weeks, she has also called for the black flag of ISIS to be raised over Downing Street and claimed she is 'excited' at the thought of U.S. soldiers being 'slayed' if an invasion took place.She has even encouraged other Britons to travel to Syria, saying: 'I might be only 18 but I know coming to shaam [is] the best decision. Staying in the UK completely diminishes your islam.'The jihadist set up her Twitter account on June 27 - just one day after schoolgirl sisters Salma and Zahra Halane fled to Syria.The 16-year-old twins, who have 28 GCSEs between them, ran away from their family in Chorlton, Greater Manchester, on June 26 for 'paradise' in the war-torn Middle East.They have vowed never to return home after following their brother to Syria, and are said to have already married ISIS fighters. (dailymail.co.uk)Bakudaily.Az