"Heaven has no rage like love to hatred turned, nor hell a fury like a woman scorned," said William Congreve in "The Mourning Bride" (1697).

A mother-of-two has been sentenced to spend three years and nine months in jail after she slashed off a part of his ex-lover's penis. She also stabbed him a number of times in the neck and groin, eventually killing him.

Jian Chen has attacked her younger's son father after he made threats to separate her from her son over a disagreement. This was on top of Chen's many underlying issues with her former lover.

The NSW Supreme Court determined Chen was suffering from a "substantial [mental] impairment" when the incident happened.

Jin Xiang Peng was conscious when Chen cut off his penis, the court heard. Chen first drugged his soup with sleeping pills before she bound his wrists and feet and went on to stab him. This happened at her North Ryde home on February 9 last year.

The judge said Chen's act was neither premeditated nor impulsive. She mutilated Peng's penis and flushed it down the toilet to make sure he would not be able to recover it. This shows conscious planning on her side.

Justice Schmidt found Chen's "capacity to understand events, or to judge whether her actions were right or wrong, or to control herself, were substantially impaired."

However, Justice Schmidt said "her illness does not excuse what she has done."

Chen was given a maximum sentence of six years and nine months.