Crown prosecutor Brian Dickey told the jury the couple's relationship had deteriorated to such a degree she called her brother to tell him she was leaving the defendant and was going to write a will directing her assets to her family rather than her partner.
Liu told police Ms Chen had gone for a walk alone that evening but the Crown disputed his version of events.
"She never went out for that walk that night. It's likely, although we don't have to establish it, that she died at home by the actions of the defendant," Mr Dickey said.
Ms Chen's body was eventually found 16 months after her disappearance in a stream in a reserve in Totaravale, 10km away from their home.
After four weeks in New Zealand, Philip and Peter Chen told Liu - in recorded conversations - they believed he was responsible for their sister's disappearance and begged him to tell them where the body was hidden.
"All I want is to find my younger sister's body, for me to take her away timely. So, where on earth did you put her?," Philip Chen asked.
Liu denied he had anything to do with it.
The brothers also probed him on an alleged motive.
"It was murder for money. It's simply for that bit of money; for the two houses which you and Chen Bin [Cissy] diligently saved up for," Philip Chen asked.
"I think you ought to hand Cissy over if you have a conscience. Money is not an issue."
But Liu was adamant there was nothing in the theory.
"Why kill her? Does killing her enable someone to take her assets? Impossible. Merely for those assets? Really ridiculous," he responded.
"I place minimal value on money."
Liu was keen to assure them greed had nothing to do with Ms Chen going missing and in their final recorded conversation on December 4, 2012, he promised to have a lawyer prepare a document agreeing to pass his partner's assets on to her family - if she was found dead.
"If you are to keep what's not yours, then you will suffer a lifetime, and the next lifetime," Philip Chen said.
"It's a curse."
The trial, before Justice Sarah Katz and a jury of six men and six women, is scheduled to last eight weeks.
