London, June 5: An 18-year-old woman has become the UK's youngest convicted female Islamic State terrorist after a court found her guilty of plotting a terror attack on the British Museum here with the country's first all-woman cell. Safaa Boular was accused of planning to travel to Syria to join IS militants and later preparing to carry out a terrorist attack in London after her fiance, an Islamic State fighter, died.

A jury at the Old Bailey yesterday found her guilty of two offences of preparation of terrorist acts, the BBC reported. She was also found guilty over an earlier attempt to travel to Syria for terrorism. Her 22-year-old sister Rizlaine has already admitted planning a knife attack on London and their mother Mina Dich, 44, has pleaded guilty to assisting her.

Boular will be sentenced in around six weeks time, the report said. During her trial, the court heard how Boular - then 17 - plotted a gun and grenade attack at the British Museum. The sisters and Dich discussed their plans using Alice in Wonderland coded language, with Rizlaine as the Mad Hatter. Aged 16, Boular was radicalised online in the wake of the 2015 Paris terror attacks. She met IS fighter Naweed Hussain on Instagram and after three months of chatting, she declared her love for him with an online marriage ceremony.

The court heard how she had wanted to join Hussain in Syria, but her plan was thwarted when British security services confiscated her passport. Boular told the police about Hussain and security services deployed officers to pose as fellow extremists and speak to the pair online. On April 4, 2017, it was a security services officer, posing as an IS commander, who told Boular that Hussain had been killed in a drone attack.

The prosecution claimed this only strengthened her determination to carry out an attack in the UK. Boular went on to tell officers posing as extremists about plans for an attack and on April 12, she was charged with preparing terrorist acts in Syria. Despite being in custody, Boular continued to talk to her sister and mother about an Alice in Wonderland-themed tea party - code for an attack. In one call Boular complained: "Mate, you guys are partying without me." Rizlaine and Dich carried out reconnaissance of major landmarks in Westminster and bought knives and a rucksack, the court was told. They were arrested on April 27, the date of the planned attack, along with a friend, Khawla Barghouthi.