She is accused of sending herself a text message purporting to be from Mr Nisbet that read: "I'm sorry honey, I can't keep going on like this."
The trial has already heard that Milner asked co-workers a few months before her husband's death whether rat poison could kill a person.
They laughed off her "whacky" conversations, even joking that she may have laced muffins she brought in to work with poison.
Yesterday the first police officer on the scene of Mr Nisbet's sudden death raised concerns over the "convenience" of Milner receiving a texted suicide note in front of him.
Sergeant Christopher Barker called in his superiors, citing "some concerns about how things had been unfolding" at the scene.
They thought Milner's prolonged display of hysteria amounted to an "unnatural reaction".
Despite the initial fears of the attending officers, police originally ruled Mr Nisbet had taken his own life.
However, after a coroner raised doubts over the death, a homicide probe was launched and more than two years later Milner was charged with murder.
The Crown alleges Milner was determined to kill her husband and cash in a $250,000 life insurance policy.
It's alleged she plotted the best way to do it, asking friends and workmates for views on poisoning methods, and offering to pay a hitman $20,000.
The trial, before Justice David Gendall, continues.
