US citizen Jamie Paulin Ramirez, 32, pleaded guilty before US District Court Judge Petrese Tucker in Philadelphia to one count of conspiracy to provide material support to terrorists.
She faces a 15 year imprisonment and a USD 250,000 fine at sentencing.
Ramirez, who has been in custody since her arrest in April last year had initially pleaded not guilty.
She was first charged in a superseding indictment in April 2010, along with co-defendant and Pennsylvania resident Colleen LaRose, who went by the name of Jihad Jane.
According to documents filed with the court, Ramirez and LaRose conspired to obtain military-style training in South Asia and then travelled to and around Europe to participate in "violent jihad".
The duo was also said to have been involved in a plot to kill Swedish cartoonist Lars Vilks who depicted Prophet Mohammed in a blasphemous cartoon.
LaRose, 47, had pleaded guilty to terrorism charges on February 1 this year. "Today's guilty plea by Jamie Ramirez, coupled with that of Colleen LaRose last month, underscores the evolving nature of the terrorist threat we face," said acting Assistant Attorney General for National Security Todd Hinnen.
Ramirez exchanged e-mail messages with LaRose during the summer of 2009, in which LaRose invited her to join her in Europe to attend a training camp.
In an August 2009 email, LaRose told Ramirez that "soon I will be moving to Europe to be with other brothers and sisters... when I get to Europe, I will send for you to come be with me there... This place will be like a training camp as well as a home."
Ramirez travelled to Ireland in September 2009 with her child with the intent to live and train with jihadists.
She married a co-conspiartor in Ireland, whom she had never met before, "in an Islamic ceremony" knowing that her presence in Europe, her marriage and her future actions would provide support for the conspiracy, the FBI statement said.
The co-conspirator recruited another individual to find "brothers and sisters" to go to a "camp for (military-style) training... and then come back to Europe to do the job... The job is to knock down some individuals that are harming Islam."
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