Police allege 46-year-old former lawyer Emma Walters tried to obtain a gun through a third party and made threats to kill.
She has been charged with incitement to commit conspiracy to murder the Victorian construction union boss.
She has been bailed from a Melbourne court and will reappear on April 5.
Walters and Setka have been embroiled in a long legal battle, involving allegations of domestic abuse against Setka. He denies the allegations.
