Trio...

A British teenager was sentenced to prison for life as the youngest woman to be convicted of plotting a terror attack on British soil.

Safaa Boular, 18, of Vauxhall, London, was convicted of preparing acts of terrorism and attempting to travel to Syria to join Islamic State militants.

She had been groomed online for terrorist activity by her fiancé. She originally hoped to marry in Raqqa, the ISIS proclaimed capital in Syria, but was prevented from traveling there by police in April 2017. Hussain, 32, died in an airstrike.

In passing sentence, Judge Mark Dennis QC told Boular her views were "deeply entrenched" and "she was old enough to make her own decisions, and her own choices," the BBC reports.

Her older sister and their mother have already been jailed for plotting a knife attack in Westminster, The Independent reports.