(Reuters) - A U.S. judge on Thursday sentenced a Mississippi woman to 12 years in prison for providing material support to Islamic State after she and her husband conspired with an undercover FBI employee to travel to Syria and aid the group's media campaign.

Jaelyn Delshaun Young, 20, had pleaded guilty to one count in March as did her co-defendant and husband, Muhammad Oda Dakhlalla, 23.

Judge Sharion Aycock of the Northern District of Mississippi imposed a 12-year sentence and ordered Young to serve 15 years of supervised release once she is released from prison, the U.S. Justice Department said in a statement.

Dakhlalla is due to be sentenced on Aug. 24.

Theirs are two of dozens of criminal cases against U.S. citizens related to their support of Islamic State, which is also known as ISIS or ISIL or Daesh and is listed as a foreign terrorist organization by the U.S. State Department.

Young and Dakhlalla were arrested at a Mississippi airport in August 2015 while attempting to board a flight to Turkey.

Young acknowledged her role as the "planner of the expedition" in an incriminating farewell letter, according to court documents filed by U.S. prosecutors.

Young's Twitter posts about her desire to join the militant group caught the attention of the Federal Bureau of Investigation in May 2015, and an agent posing as an Islamic State recruiter began corresponding with her and Dakhlalla.

Young and Dakhlalla told the purported recruiter they would help Islamic State "correct the falsehoods" about it in U.S. news media, such as reports that the group trades young girls as sex slaves, according to court records.

They also asked the recruiter whether Islamic State would offer Koran classes in English, how they would be required to prove they were Sunni Muslims, and what kind of military training Dakhlalla would receive.

According to court records, the couple, who had an Islamic marriage but did not get their union legally recognized, were motivated to join the group after viewing Islamic State executions of people they deemed immoral, and because they perceived the group as "liberators" of parts of Syria and Iraq.

(Reporting by Daniel Trotta; Editing by Richard Chang)