Hong Kong (CNN) A Hong Kong housewife has been sentenced to six years in prison for abusing a young Indonesian worker she kept prisoner in her home.

In delivering her sentence, the judge said 44-year-old Law Wan-tung was a bully who showed contempt for those beneath her.

Earlier this month, the mother-of-two was found guilty of 18 of 20 charges of abuse involving 23-year-old Erwiana Sulistyaningsih , and one other domestic worker.

The court heard Law regularly beat Erwiana with mop handles, coat hangers and, on at least one occasion, shoved a rod from a vacuum cleaner into her mouth. The abuse only ended when Law drove her employee to Hong Kong International Airport with a one-way ticket home.

She instructed Erwiana to wear six layers of clothing and a diaper so the abuse wouldn't be detected. However, other Indonesian women noticed her injuries at the airport and urged her to call police.

Surrounded by supporters yelling "No reform, no justice" and "We are workers, we are not slaves," Erwiana attended court to see her abuser sentenced. She said she was disappointed with the duration of the sentence but happy that the ruling had shown that "slavery in Hong Kong really exists."

Not a 'callous monster'

During the sentencing hearing, Law's lawyer conceded it was a bad case of abuse "but not the worst of its kind."

Graham Harris said Law had very high standards of cleanliness due to her son's skin allergy and that Erwiana had failed to meet her expectations.

Describing his client as a "doting mother," Harris said Law had been "vilified, demonized and ostracized," and was not the "callous monster" as portrayed by some during the case.

'A simple young lady'

When the trial ended, Judge Amanda Woodcock described Erwiana as "a simple young lady who tried to financially better her life and that of her family."

Erwiana thought she was under surveillance at all times, and believed Law's threats that her family would be killed if she told anyone about the abuse. "They made her compliant and more subservient," Woodcock said.

Photos: Maid abused in Hong Kong Photos: Maid abused in Hong Kong Former domestic worker Erwiana Sulistyaningsih arrives at a Hong Kong court on Tuesday, February 10, ahead of the verdict in an assault case against her former employer. Hide Caption 1 of 8 Photos: Maid abused in Hong Kong Erwiana stands in front of her family house in Kawis, Indonesia, on April 25 after her successful recovery from months of abuse by her Hong Kong employer. Hide Caption 2 of 8 Photos: Maid abused in Hong Kong A doctor checks Erwiana before she leaves the hospital in Sragen, Indonesia, on February 5, 2014. Hide Caption 3 of 8 Photos: Maid abused in Hong Kong Erwiana lies on a hospital bed before leaving on February 5, 2014. Hide Caption 4 of 8 Photos: Maid abused in Hong Kong Police escort Law Wan-tung to her home in Hong Kong for further investigation on January 21, 2014. Hide Caption 5 of 8 Photos: Maid abused in Hong Kong Erwiana is interviewed from her hospital bed in Sragen by authorities on January 21, 2014. Hide Caption 6 of 8 Photos: Maid abused in Hong Kong Erwiana rests at a hospital in Sragen on January 15, 2014. Hide Caption 7 of 8 Photos: Maid abused in Hong Kong Erwiana receives treatment at a hospital in Sragen on January 15, 2014. Hide Caption 8 of 8

During the trial it emerged Erwiana slept on the floor, moving the vacuum cleaner and bags of books to clear enough space to stretch out.

She was only permitted to sleep between 1 p.m. and 6 p.m., when she was woken to resume work cleaning Law's home.

She was only given meager rations and one day, knocked on a neighbor's door to ask for food. The neighbor shut the door. Erwiana said Law's children overheard and told their mother who then threatened her again.

Law's children -- her 18-year-old son Edmund Tsui Wing-kit and 16-year-old daughter -- referred to only as "Kelly" to protect her identity -- testified that they didn't see or notice the abuse that went on in their home during the seven months Erwiana worked there.

Calls for better protection for domestic workers

Erwiana's case was held up by campaigners for Hong Kong domestic workers as an example of how the law fails the city's 320,000 foreign domestic workers. The majority are women, from the Philippines, Indonesia, Thailand and other Asian nations.

Last April, Erwiana was named by Time magazine as one of the world's 100 most influential people , which commended her bravery for drawing attention to "the plight of a vulnerable, often invisible population."

Campaigners say rules dictating that domestic workers reside at their employers' homes expose foreign domestic workers to potential abuse. They say they're often trapped in abusive situations because they're only given two weeks after leaving one contract to find a job or face deportation.

'Stop the exploitation'

The Hong Kong government started allowing foreign domestic helpers to work in the Chinese territory in the 1970s to fill a shortage of local staff. Many come via agencies direct from their home countries and don't meet their employer before signing a two-year contract.

They're paid a minimum wage of HK$4,110 ($530) a month and by law are only entitled to one day off a week.

Amnesty International says Erwiana's case should serve as a "wake-up call" for the government to stop the "widespread exploitation" of domestic workers.

"The Hong Kong authorities can no longer bury their heads in the sand and dismiss horrific abuses as isolated incidents," said Norma Kang Muico, Amnesty's Asia-Pacific migrant rights researcher.

After the verdict, Hong Kong's Secretary for Labour and Welfare Matthew Cheung said the government welcomed the judgment, which he said underlined "the importance that the Government and the court attach to protecting the labor rights as well as the well-being of foreign domestic helpers in Hong Kong.

"We attach great importance to protecting their well-being, and ensure that their labor rights are fully respected," Cheung said.