MOMENTS after she stabbed her boyfriend to death on Christmas Day, a NSW Central Coast woman sent a text message telling another man she was going to eat the body because "I think he tastes good".

In the NSW Supreme Court today, Tamie Melehan admitted to killing her boyfriend, but pleaded not guilty to murder by reason of mental illness.

David Vaughan, 30, suffered 16 stab wounds to his neck, six to his chest and four to his abdomen during the frenzied knife attack by his girlfriend of three months at her apartment on December 25, 2008.

An autopsy revealed his jugular veins had been slashed on both sides of his neck and he died from those "rapidly fatal" injuries.

As her murder trial was about to begin, Melehan, 29, admitted to the actions which caused Mr Vaughan's death, but pleaded not guilty for reasons of mental illness.

Melehan has a long history of mental illness and was diagnosed with paranoid schizophrenia in 2002, the court heard.

Prosecutor Michael O'Brien said that at the time Mr Vaughan was killed, Melehan sent another man a series of text messages telling him she missed him and inviting him over to feast on her boyfriend's "delicate meat".

"Oi, can I eat this fella?" she said.

"I think he tastes good ... there's enough to go around if you want to join in - no joke, delicate meat ...

"Dear me, need help to get rid of the body."

A little later she phoned her mother saying: "Can you come over and get him before I slit his throat?"

Melehan's mother, Loretta Watts, arrived at her daughter's home to find Mr Vaughan dead on the floor of the shower with blood gurgling out of a slash wound in his neck.

Mr O'Brien told Justice Monika Schmidt there was ample psychiatric evidence to support claims that Melehan was suffering "an acute exacerbation of her chronic mental illness" and was acting in "a delusional way" at the time of the attack.

"The Crown submits on the evidence that is before your honour, your honour would make a finding that the accused is not guilty of the offence within the grounds of mental illness," he said.

Justice Schmidt adjourned proceedings and is expected to give her decision soon.