Pennsylvania resident Colleen LaRose, 46, smiled and appeared relaxed as she denied conspiracy to support terrorists, recruiting militants, and agreeing to murder a Swedish cartoonist who had offended some Muslims.
The federal court judge in Philadelphia ordered Rose, whose blonde hair was done up in dreadlocks and a pony tail, to be held without bail until her trial starts May 3rd.
If found guilty she faces up to life in prison.
The rash of cases of so-called home-grown terrorists is a relatively new phenomenon in the United States.
LaRose's case is seen as indicating an alarming new development in which militants are drawn not from Muslim immigrant communities but from Americans born and raised in the United States.
In Chicago, another US citizen, David Coleman Headley, was expected to plead guilty Thursday to scoping out targets in India for the deadly 2008 Mumbai attacks and plotting to attack a Danish newspaper.
Headley was born Daood Gilani to a Pakistani father and American mother, but later changed to his mother's maiden name and adopted a Western first name, allowing himself to blend in more easily.
LaRose allegedly boasted in Internet traffic, where she went by the monikers "Fatima LaRose" and "JihadJane," that her looks allowed her to go anywhere undetected.
Her alleged recruitment drive targeted women with the kind of mobility to escape initial suspicion. They were to possess "passports and the ability to travel to and around Europe in support of violent jihad," the indictment says.
She is accused of trying to transfer a stolen US passport "to facilitate an act of international terrorism."
The two further suspects alleged to be involved in the Vilks murder plot, a 45-year-old Algerian and a 33-year-old Libyan, will also face a court in Waterford, Ireland on Friday.
The pair are both currently remanded in custody, but on charges unrelated to the Vilks case. Further suspicions could be levelled against the men in court on Friday to support additional charges, on which an indictment must be brought within 40 days.
The Iranian government has now also entered the controversy over the Muhammad cartoons, which were originally published by the local Örebro newspaper Nerikes Allehanda in 2007 to accompany an editorial on freedom of expression.
After the alleged plot to kill Lars Vilks became known on March 9th, leading Swedish newspapers re-published the caricatures as a gesture of support for the artist, who has a $100,000 bounty on his head from an al-Qaeda linked group.
Iran has echoed calls from Malaysia for the Swedish government to act on what it considers a "desecration of Islam", adding its voice to a chorus of international disapproval, which also includes Pakistan and Egypt.
Malaysian foreign minister Anifah Aman denounced the publication of the cartoons in an unusually candid speech on Saturday, calling for the Swedish government to intervene against the newspapers.