LONDON (AP) — A London teenager went on trial Thursday for allegedly plotting a grenade attack on the British Museum after failing in her ambition of becoming a jihadi bride in Syria.

Prosecutors say Safaa Boular plotted the attack in messages exchanged with an older Islamic State group fighter in Syria. She hoped to marry him, but he was killed in 2017.

Prosecutor Duncan Atkinson told jurors at London's Central Criminal Court that Boular planned to "unleash violence and terror in the heart of London" by attacking the world-famous museum.

The 18-year-old denies planning acts of terrorism.

Atkinson said after Boular was arrested in April 2017 for trying to travel to Syria, she tried to enlist her 21-year-old sister Rizlaine to carry out an attack. In phone calls from prison, she used code words that referred to an attack as an "Alice In Wonderland"-themed tea party, the prosecutor said.

He said Rizlaine and the siblings' mother, Mina Dich, carried out reconnaissance around major London landmarks and bought a pack of knives and a knapsack. The pair were arrested later the same month.

Rizlaine Boular has admitted planning an attack and has pleaded guilty to the charges. Dich is accused of assisting her.