A 41-year-old woman accused of coercing a close co-worker into prostitution over the course of three years has been sentenced to 13 years in prison by an appellate court on Wednesday, after a lower court sentenced her to 10 years.

The defendant, who worked with the victim between October 2019 to September 2022, has been accused of forcing 2,500 accounts of prostitution on the victim, and pocketing the 500 million won ($380,000) profit made from the illegal acts.

The police's investigation found that the defendant exploited the victim's fondness for her to gaslight the victim for years. Gaslighting refers to psychological manipulation in which the victim is led to doubting his or her own perceptions, rendering him or her unable to make autonomous decisions.

"Her crime is malicious in nature, as she forced a co-worker to engage in prostitution and extorted a great amount of money," the court said in its verdict.

The defendant was also ordered to pay 215 million won to the government and complete 200 hours of mandated treatment for sex offenders. She was also banned from getting a job at any organization related to children.

The husbands of the defendant and the victim were also accused of being accessories of the crime, and were each sentenced to six years in prison and fined 147 million won.