Unhappy with her former girlfriend, a doughnut shop employee and three men assaulted the woman in a Marsiling flat and kept her there for nine days.
The 34-year-old victim was made to do household chores and had to sleep on the living room floor.
Noorfarahain Mohd Noorudin also forced her former girlfriend to strip, took a photograph of her and threatened her with it.
She told the victim: "This is your dignity. So remember before you want to do anything. If you try to run away, I will make the photo viral on the Internet."
Noorfarahain, 27, was sentenced yesterday to three years and two months' jail after pleading guilty to one count each of assault, criminal intimidation, extortion, wrongful confinement and methamphetamine consumption.
She must spend an additional six weeks behind bars in lieu of caning for the extortion charge.
Eight other charges, including a second extortion charge involving $100, were taken into consideration during sentencing.
The court heard that the two women were in a romantic relationship between November 2016 and November 2017. In January last year, Noorfarahain, who is a divorcee, entered into a relationship with her own cousin, Muhammad Indra Mohamed Yusli, 23.
On Feb 9 that year, the victim told Noorfarahain she would go to the Marsiling flat to look after the younger woman's son, Deputy Public Prosecutor Tan Yen Seow said.
The court heard that when she reached the unit at around 2am, she was confronted by Noorfarahain, Indra and two other men. She was accused of making Noorfarahain's life "miserable" and the group assaulted her.
The DPP told District Judge Salina Ishak: "The accused took all of (the victim's) possessions, including her wallet and mobile phone. Indra told the woman that she was not allowed to leave the flat until she recovered from her injuries."
A week later, Noorfarahain ordered the victim to undress before snapping the picture of her in the nude.
The next day, she used her former girlfriend's mobile phone to send a message to the woman's mother, asking for $3,000. The mother agreed to transfer $200 to her daughter's bank account.
Noorfarahain later asked her former girlfriend to withdraw the money and pass it to her. The victim complied as she feared that Noorfarahain would upload her nude picture onto the Internet.
On Feb 18 last year, the victim was told to go to the flat belonging to Noorfarahain's mother on her own. At around 12.45am the next day, the victim went to Yishun North Neighbourhood Police Centre.
Noorfarahain was arrested at around 4.15pm that day and traces of methamphetamine were found in her urine sample.
The judge yesterday ordered Noorfarahain to pay her former girlfriend $300 in compensation.
The case involving Indra is still pending while the other two men have not been charged.