The sister-in-law of the couple who carried out the San Bernardino terror attack changed her plea to guilty Thursday in her family's marriage-fraud case.

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Tatiana Farook pleaded guilty in Riverside, Calif., to one felony count of conspiracy that included lying to federal agents and in legal documents. She faces a maximum of five years in prison during sentencing scheduled for later this year.

Her husband, Syed Raheel Farook, is the brother of Syed Rizwan Farook, who launched the December 2015 terror attack with his wife, Tashfeen Malik. The couple killed 14 people and wounded 22 others, sparking a manhunt before a police shootout that killed them.

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The marriage-fraud case involves Tatiana's sister, Mariya Chernykh, a Russian immigrant whose sham marriage to a Riverside man was discovered when her husband became part of the shooting investigation.

Chernykh pleaded guilty in the case last month.

Since the attack, investigators have said Enrique Marquez, a friend of Farook’s, provided the guns the terrorists used. Marquez pleaded not guilty to conspiring with Farook on an unrelated plot.

"After today's guilty plea, all but one of the defendants charged as a result of the December 2 San Bernardino terrorist attack have been convicted," U.S. Attorney Eileen M. Decker responded. "These convictions are a testament to law enforcement's ongoing commitment to ensure that everyone related to the terrorist attack are brought to justice."

Fox News' Will Carr, Corbett Riner and The Associated Press contributed to this report.