Shannon Conley
Shannon Conley during US Army Explorer training Facebook

An American teenager arrested at Denver International Airport as she was trying to join the Islamic State (also known as Isis) in Syria has pleaded guilty to terror charges in federal court.

Shannon Maureen Conley, 19, admitted to providing material support to IS and other al-Qaida offshoots in the Middle East before the Denver's US District Court. The woman appeared in court donning a green hijab over a grey and white Jefferson County jail jumpsuit.

Her public solicitor said that Halima, Conley's Muslim name, was fully aware that her arrest may have saved her life and regretted her involvement with jihadists. "Unfortunately, as she pursued the study of that faith she was led terribly astray. That in turn led to her making some very poor choices. She is now paying the price of those choices," Robert Pepin, her lawyer, told the Denver Post.

The FBI started investigating Conley, a Muslim convert, in November 2013 after she was seen stalking the Faith Bible Chapel of Arvada. The woman reportedly used to take notes and sketches of interior rooms of the church and the layout of the campus. Staff approached Conley and asked her to see the notes, but she refused and became confrontational.

She reportedly told them "Why is the church worried about a terrorist attack?", claiming that terrorists are "not allowed to kill aging adults and little children".

Faith Bible officials are sensitive about security in the campus because of a shootout in 2007, in which two people were gunned down by a man named Matthew Murray at the church's Youth with a Mission training centre. The church senior pastor George Morrison called Conley a "terrorist wannabe" and phoned the FBI.

During interviews with FBI agents in November, Conley, who had received military training in a Texas camp run by the US Army Explorer, said she hated members of the Faith Bible Chapel and disliked their support for Israel and Israel itself. In her war against "kafir" (a derogatory term for non-Muslims), she felt it was acceptable to harm innocents if they are part of a target.

Despite repeated FBI warnings, the woman refused to back down and was arrested on 8 April as she attempted to board a Turkey-bound plane to join and marry a 32-year-old Tunisian man who was waging jihad in Syria. She met the man on Skype.

In her house, agents found several DVDs of a senior al-Qaida leader named Anwar al-Awlaki, who acted also as recruiter for the Islamist group. He was killed in Yemen by a Cia-led US drone.