When all attempts to save her marriage seemed futile, Tan Siow Yee, 39, resorted to slashing her husband's alleged mistress with a pen knife.

The attack in April has now left Madam Khoo Bee Lay, 44, with permanent scars on her left cheek and nose.

On Friday, a district court sentenced Tan to three month's jail for hurting Khoo with a 5cm-long foldable knife blade.

Standing head bowed in the dock, Tan could not control her emotions and a constant stream of tears was seen flowing from her eyes. She is the mother of three teenage children.

District Judge Jeffrey Sim said: 'I accept that there are strong mitigating factors. However, I cannot ignore the fact that the offence committed is a serious one.'

She could have been sentenced to a maximum of seven years' jail and fined.

According to court documents, Tan went to a karaoke pub along Upper Bukit Timah Road on April 22 to look for her husband Mr Yeo Chor Boon, 42, a logistics supervisor.

When she got there, she spotted her husband having an intimate conversation with Madam Khoo. An argument ensued and Tan downed an alcoholic drink.

When Mr Yeo asked Tan to talk in his car instead, she agreed and went to the toilet first.

However, when she returned, she realised that her husband and Madam Khoo had already left the pub.

A waitress told her that her husband had gone to his car and when she went to look for him. She saw Madam Khoo sitting beside her husband in the front passenger seat of the locked car.

Infuriated, Tan asked Madam Khoo to get out of the car but she refused. Instead Mr Yeo asked Tan to sit in the back passenger seat if they were going to have a conversation.

Mr Yeo subsequently wound down the left rear window of the vehicle.

It was then that Tan pulled out the penknife from her handbag and slashed Madam Khoo on her face through the open window.

In mitigation, her lawyer Mr Kelvin Lim said that the attack was not pre-meditated.

He said that his client had always kept the penknife in her bag as she is an avid angler and uses it to cut bait.

'She had also used the same penknife to cut herself on the wrist two years who when she first discovered her husband's extra-marital affairs,' added Lim.

Madam Khoo was taken to Alexandra Hospital after the attack and later referred to the National University Hospital for plastic surgery. Tan took a taxi to Madam Khoo's flat in Petir Road and called the police who arrested her.

She later told police that although she consumed an alcoholic drink, she still knew what she had done.

Madam Khoo is still receiving laser treatment for her scars, the court heard.