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.
Dobson sagged in the dock and burst into tears at the High Court in Edinburgh as Lord Boyd of Duncansby imposed an extended sentence, ordering her to be supervised for a year upon 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 this was a deliberate and wicked act of the utmost 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."
The sentence was backdated to January 13, this year.