A maid, who was tasked to feed her employer's elderly mother, slapped the 88-year-old woman - who has dementia - three times when she refused to eat and spat out some of the food.

Tarminah, whose name has only one word, also pulled Madam Sim Hong Kim's right ear twice and stopped only when the octogenarian, who uses a wheelchair, pushed her hand away.

Madam Sim's daughter, Ms Quah Cheng Yip, 64, witnessed all this on her cellphone.

She watched in real time the Indonesian committing the offences on Aug 7 last year. They were captured by a closed-circuit television camera installed in her Jurong West home.

Ms Quah alerted the police and the maid was arrested.

Tarminah, 38, was yesterday jailed for four months after pleading guilty to an assault charge.

Deputy Public Prosecutor Ng Jun Chong said the maid had been tasked to help look after Madam Sim.

Tarminah became angry while feeding the elderly woman and assaulted her.

The DPP told District Judge Ong Chin Rhu: "While wiping the victim's mouth, the accused slapped the victim twice on her right cheek before slapping her once more on her left cheek, causing the victim bodily pain.

"The accused then wiped the victim's face with a piece of cloth before pulling the victim's right ear twice. The accused only stopped pulling the victim's ear when the victim pushed her hand away."

After the assault, Madam Sim was taken to Ng Teng Fong General Hospital, where she was found to have a bruised left arm.

For assault, Tarminah could have been jailed for up to two years and fined up to $5,000.