Demi Harris, 20, was woken by revellers to see her partner Christopher Pearson, 39, had stripped off along with two other naked men and a young woman in her underwear, prosecutor Michael Auty QC told a jury at Nottingham Crown Court.
Harris poured chlorine into the hot tub, in the back garden of their Strathmore Close address, in the early hours of Sunday, February 18.
He said that Harris armed herself with a blue kitchen knife and ran upstairs, followed by Mr Pearson.
Moments later a female guest found Harris on the landing saying “What have I done?” as her partner lay on the floor, with part of his bowel hanging out, mumbling “What’s happened?”
“She said: “I have gone too far this time,”” said Mr Auty. “And in these few words she encapsulates so accurately, the prosecution case.
“Harris instantly knew he was close to death and repeatedly said: “He is going to die.””
He said Harris claimed he caught her by the ankle at the top of the stairs and was thrown into the bedroom where she found the knife, but that made “no sense” as Mr Pearson kept a machete there.
She later told police he had grabbed her hair, but there was “no mark, not even a missing hair” on her.
Harris said she had done no more than “jab him twice” with the tip of the blade as she tried to get past, but the wounds did not bear this out.
A 999 call at 5.50am, demonstrated the “secret world beyond the reach of the authorities” in which the pair lived, Mr Auty said.
Mr Pearson was rushed to the QMC Hospital, but three blood transfusions couldn’t save his life and he was pronounced dead at 12.39pm.
A post-mortem revealed the membrane which holds the intestine in place had been punctured, causing massive blood loss, and a second wound had passed through his body.
Mr Auty said parties were a regular feature at their semi-detached home, which had been adapted to include a bar and pool table, and the couple were “popular with everyone except for their neighbours.”
On this occasion they had invited around 15 people back, after the bars shut in Hucknall.
He described Harris as “manipulative and conniving”, who was far from being a “cowed and broken wretch” in the three-year relationship.
“They were separated by many years in age but in many ways they were ideally suited,” he said. “The violence and aggression that occasionally erupted were part and parcel of their relationship.”
He said Harris relished the “opulent lifestyle” which Mr Pearson provided for her, and she “savoured the power and status it gave her.”
He described the couple as a “potent and effective force” who withstood interference from the police and others.
“Mr Pearson was not some sort of saint,” he concluded. “But he didn’t deserve what happened to him.”
Harris, who wore a black suit and white shirt, made notes throughout the opening statement.
Her defence case, which will be given by Sallie Bentley-Jenkins QC, was delayed until Friday. The trial continues.