FARMINGTON — A Farmington woman pleaded guilty Wednesday to stabbing a man in the stomach on the Navajo Nation in November 2011.

Thelda Frank, 43, will be sentenced to 18 months in prison as a condition of her plea agreement, according to a news release from the U.S. Attorney's Office for the District of New Mexico.

Frank assaulted a man with a knife on Nov. 27, 2011. The assault, which left the man with serious injuries, happened on the Navajo Nation, but court documents did not state the exact location or the victim's name.

Frank was arrested in January 2013. Court documents don't explain why she was not arrested for more than a year after the assault.

The FBI and the Navajo Nation Division of Public Safety investigated the case.