Businesswoman Sarina Russo has told a Brisbane murder trial her longtime friend Maureen Boyce was "very happy" the night before she died and was excited to become a grandmother.
Thomas Chris Lang has pleaded not guilty to murdering former model Ms Boyce at her Kangaroo Point apartment in October 2015.
The New Zealand-based doctor is accused of killing the 68-year-old socialite with a kitchen knife out of jealousy because she would not leave her husband.
The court heard today the issue in the trial would be whether Mr Lang killed her or she took her own life.
Ms Russo told the Supreme Court she first met Ms Boyce in 1979 when they were neighbours in Highgate Hill and she respected her so much she asked her to be her business partner.
Ms Russo's nephew married Ms Boyce's daughter Angelique in 2015.
"It was a joyous occasion until she was murdered," she said.
Ms Russo was then urged to avoid such conclusions and Justice Peter Flanagan told the jury to disregard her comment.
"When a witnesses uses those words 'murdered' or 'killed' to describe the death of Maureen Boyce, they are inadmissible conclusions which you should utterly ignore," he told the jury.
Ms Russo said the night before Ms Boyce's death, she was having a home massage when her friend called her "very upset" about being unable to sell her penthouse.
She said Ms Boyce asked her: "How do you cope with the stresses of your life?"
But she said Ms Boyce's mood eventually changed and she left the conversation sounding "very happy" and made plans to attend Ms Russo's mother's 102nd birthday the following week.
During cross-examination, defence barrister Tony Glynn questioned Ms Russo about a statement she made to police following her friend's death.
Mr Glynn asked: "You would describe Maureen as being a fragile person with [an] extreme mental health disorder?"
Ms Russo replied: "Yes."
The trial continues.
