Shaniece Dobson armed herself with a kitchen knife and stabbed Sean Martin, 21, in the chest a year ago in Coatbridge, North Lanarkshire.
He died within minutes of receiving the blow.
First offender Dobson, 21, was originally charged with murder but was convicted by a jury of the reduced charge of culpable homicide.
At the High Court in Edinburgh today, Lord Boyd of Duncansby imposed an extended sentence, ordering Dobson to be supervised for a year upon her release from prison.
The attack on Mr Martin, reported to be her boyfriend, took place on February 25 last year.
Passing sentence, the judge told Dobson: "For no reason that this court can discern exactly one year ago today you deliberately walked into the kitchen of your flat, armed yourself with a kitchen knife, walked back out into the living room and stabbed Sean Martin in the chest using such force that it penetrated the chest cavity to a depth of 17cm.
"It is apparent that he died within a few minutes. While the jury were not satisfied that this demonstrated the gross and wicked recklessness required to constitute the crime of murder, there is no doubt that this was a deliberate and wicked act of the upmost gravity.
"You chose to go into the kitchen, you chose to pick up the knife, you chose to go back out into the living room and you chose to stab him in an area of the body which would inflict the maximum damage.
"While the evidence showed that there may have been some argument between you and Sean, nothing that happened that night in the flat comes close to providing a justification, pretext or even explanation for your behaviour."
Lord Boyd's statement in court was released by the Scottish judiciary following the hearing.
The judge said it was "even more shocking" that the attack happened in front of the victim's younger sister and brother.
Lord Boyd said the victim's parents, Thomas and Angela, were proud of their son.
"His father speaks particularly of his success as an amateur boxer," the judge said.
"His passing has left a large gap in the family and each one of them in their own way will feel this loss. He was more than just a family member. He was a confidant and best friend.
"No sentence that I pass can adequately mark their grief. Nothing I can do can compensate them for their loss."
In passing sentence, the judge took into account the fact that Dobson was a first offender, is remorseful and has been seeking treatment for alcohol addiction.
He also pointed to the fact that Dobson had offered to plead guilty, pre-trial, to the offence of which she was ultimately convicted. Her plea had not been accepted by the Crown at that early stage.
The sentence was backdated to January 13 this year.