SHAH ALAM, Malaysia — A Vietnamese woman charged in the airport assassination of the half brother of North Korea’s leader, Kim Jong-un, was sentenced on Monday after pleading to a lesser charge of causing bodily harm.

The defendant, Doan Thi Huong, 30, was one of two women who smeared VX nerve agent on the face of Kim Jong-nam, Kim Jong-un’s elder brother, in February 2017. She was ordered to serve 40 months in prison.

But her lawyer said she would be released on May 4, after time served and an additional sentence reduction.

Her co-defendant, Siti Aisyah, 27, was freed three weeks ago after intensive lobbying by the Indonesian government, including a personal appeal from President Joko Widodo to Malaysia’s prime minister, Mahathir Mohamad.

Both women said that they had been tricked by North Korean agents into thinking that they were participating in a harmless prank for a reality show and that they had no intention of killing Mr. Kim.

Ms. Huong appeared to be crying during much of a court hearing on Monday where she entered her plea. But she left court smiling broadly.

The judge in the case, Azmi Ariffin, told Ms. Huong in court that she was fortunate to escape a death sentence and that she should be grateful to prosecutors and the attorney general, Tommy Thomas, for agreeing to the plea deal.

“You are a very lucky person today, because from the original charge of murder, which carries a mandatory death sentence, the prosecutor has offered a lesser charge of voluntarily causing harm with VX,” he said.

Ms. Huong’s lawyer, Hisham Teh, told reporters that he had argued that she should have been freed sooner, as her co-defendant was, because she was “naïve and gullible and was exploited.”

“The girls should not have been charged in the first place,” he said.

Ultimately, though, “we are happy because ultimately she can go home within one month,” he added.

Officials still believe that the assassination was organized by North Korean agents: four North Korean men who were believed to have orchestrated the plot and then flew out of Malaysia within hours of the killing. Three other North Koreans implicated in the attack were later allowed to leave the country.

No one other than the two women ever faced charges.

Ms. Huong’s father, Doan Van Thanh, attended the hearing and told reporters afterward: “I hope that my daughter will be released in one month. My daughter is very happy today.”