Ní Chuilín was an active volunteer in the IRA. In 1989, she was arrested after trying to place a booby-trap bomb under the gates of Crumlin Royal Ulster Constabulary station. At Belfast Crown Court the following year, she was convicted of firearm possession, possession of explosives with the intent to endanger life, and attempted murder. Ní Chuilín was sentenced to eight years in prison, but she was released after four years. She worked for ten years as coordinator of Tar Anall, a project for republican ex-prisoners.