The NSW Director of Public Prosecutions will consider whether to appeal against a 13-year sentence handed to a man who admitted killing his girlfriend.

Khanh Thanh Ly, 37, was on Wednesday sentenced to 18 years with a non-parole period of 13 for murdering his partner Miming Listiyani in April 2016, with the state's Attorney-General Mark Speakman on Thursday saying he was "concerned" about the decision after reviewing the judgment.

"Domestic violence is abhorrent. I have asked the Director of Public Prosecutions to consider if an appeal is appropriate," Mr Speakman said in a statement.

Ly pleaded guilty to murder after he was found standing over the naked body of his 27-year-old ex-girlfriend in shallow water near Cabarita Wharf in April 2016.

Miming Listiyani was murdered by her ex-boyfriend in Sydney's west in April 2016. (AAP)

The pair had been dating for about two years and had met at a Sydney hotel to exchange some personal items following a break-up.

Ly, a friend of executed Bali Nine drug smuggler Myuran Sukumaran, could not explain how the meeting ended the way it did, at a Supreme Court sentence hearing last year.

The 37-year-old's memories of the night in 2016 are "fragmented, incoherent and sporadic", the court heard.

Ly said he recalled trying to get off Ms Listiyani before "falling and just seeing black and tasting blood".

Ly leaving the Brisbane Magistrates Court in 2006 after being charged over a drug conspiracy linked to the Bali Nine. (AAP)

He was diagnosed with post-traumatic stress disorder, with the court hearing his mental health and its impact on his offending behaviour would be a key issue in sentencing.

Acting Justice Jane Mathews today told the court she had rarely come across a case where the offender was as remorseful and devastated.

"I am satisfied had he not suffered from PTSD, the offences would not have occurred," Judge Mathews said.

"This offence was completely out of character for this offender”.

Listiyani's body was found near Cabarita Wharf in 2016. (AAP)

"I have rarely come across a case where the offender is as remorseful and devastated by his actions as this one.

She went on to say that his family and friends can attest to the “extent of bewilderment, regret and sorrow for what he has done".

Ly's uncle said he was "a broken man".

To the family of Ms Listiyani, Judge Mathews said : "You’ve lost a beautiful much-loved and highly valued person who was central to your lives. You will no-doubt think the sentence is completely inadequate."

Ly and Listiyami had been dating for about two years. (AAP)