Lindy Yvonne Williams, 60, is on trial for murdering George Gerbic on the Sunshine Coast in 2013, dumping his torso on the side of a road and setting it alight.

Mr Gerbic's ex-wife Cheryl Aiken gave evidence in Brisbane Supreme Court on Wednesday, accusing him of giving her herpes when she was pregnant and having affairs during their marriage.

"At the time I was breastfeeding, George was in bed with a Swedish model," she said.

Ms Aiken told detectives in August 2014 Mr Gerbic punched and pushed her during arguments about every six months throughout their 20-year marriage up to 1994, the court heard.

The court also heard that before his death, Ms Aiken emailed a group of acquaintances about their relationship, saying: "If people knew the hell I went through, he would be in prison".

However, when she took the stand she claimed some of her statements had been embellished and he was "not actively violent all the time".

"I tend to exaggerate. That's the sort of person I am," she said.

"The reason I stayed with him 20 years was he was a very good person otherwise."

In an email to Mr Gerbric, Ms Aiken admitted being concerned about their two sons' inheritance, and at a Christmas 2010 gathering, she spoke to Williams about her financial situation.

Williams claimed Mr Gerbic may have fatally hit his head after slipping on her blood from a cut he had inflicted as she tried to defend herself during a fight in the kitchen of their Tanawha home.

In a police re-enactment played to the jury, Williams said the deceased came home angry at about 10pm, having previously told investigators he was upset by a tax issue and his ex-wife, and she served him food.

She said he flung his tray of food up after complaining his steak was tough, then lunged at her with a knife.

"I just picked the stool up, trying to hit him to get him off me," Williams said during the July 2014 re-enactment.

"I had a whole lot of blood here.

"He slips and then falls back. I don't know where he hit his head but I heard a 'bang'.

"But by this time, I'm already down to the second bedroom there."

She told police she locked herself in the bedroom, emerging the next day to see him on the kitchen floor.

She said she left and returned two days later to find his body missing its head, legs and hands wrapped in plastic in a bathroom.

Williams has pleaded guilty to interfering with his corpse after admitting to dumping the torso by Cedar Pocket Road near Gympie and setting fire to the grassy area.

Sue Brough, the wife of former Liberal federal minister Mal, also gave evidence as a Sunshine Coast-based friend of Williams and Mr Gerbic.

She said they appeared "very, very happy" together.

Australian Associated Press