Jan Charlton gave up her job as an escort
Danny O'Brien, 40 - who had been struck 20 times - was found naked, blindfolded and gagged, a jury at Leeds Crown Court was told.
Jan Charlton denies murdering Mr O'Brien at the home they shared, claiming she killed him because he threatened to kill both her and her four-year-old daughter.
But prosecutor Paul Worsley QC told the court Mr O'Brien was "executed" by Ms Charlton because she knew their "bizarre" sexual relationship was coming to an end.
Mr Worsley told the jury that Ms Charlton had been a former escort girl when she began a relationship with Mr O'Brien in September 2000.
He said: "Her relationship with Danny O'Brien offered her daughter security, financial stability, and you may think, luxury.
"Both the defendant and Danny O'Brien were highly sexed and both enjoyed an intense, and you may think, bizarre sex life. They appear to have been well suited."
Mr O'Brien's body was discovered at his large detached home at Midgley, near Wakefield, West Yorkshire, on 23 May 2001.
He had been hit more than 20 times with a large double-handed axe.
Sex toys
Mr Worsley told the jury Ms Charlton was a "callous killer and consummate actress".
Ms Charlton originally claimed to have discovered the body when she returned home to meet her ex-husband Tony who was due to pick up her daughter, the court heard.
But about five weeks after the murder she went to a police station and admitted killing him with the axe.
She told detectives she found the axe in a dressing room off the master bedroom and attacked Mr O'Brien after he said he intended to molest her daughter.
According to Mr Worsley, Ms Charlton blindfolded, handcuffed and used sex toys to try and calm Mr O'Brien down before striking him.
Self-defence
Mr Worsley said she told detectives: "Do you not understand? There was no way he was going to have my daughter and to get me."
He said she told the interviewers: "Danny fell to the floor then I just hit him and hit him and I'm just so shocked because everybody's saying I hit him 20 times."
Robert Smith, defending, formally admitted on behalf of Ms Charlton that she killed Mr O'Brien.
He said: "On behalf of Janet Charlton it is formally admitted that Janet Charlton killed Daniel O'Brien using the axe which was discovered embedded in his body.
He then told the jury they had to decide first, whether she was acting in "lawful self-defence" and then, if not, whether she was provoked.
The case continues.