Mr Justice Kay told Violet Owen, 34, he found it impossible to conclude that she intended to kill Graham Parkes, whom she loved dearly despite their stormy relationship.
Owen had not "instituted or escalated" the argument on the night Mr Parkes met his death and, before the fatal wound, had already taken steps to call police to the house, the judge told Wolverhampton Crown Court.
Reports made it clear why Owen persisted in her relationship with Mr Parkes, 30, and why she wanted the partnership to succeed. "After considerable thought to what I honestly believe is just and fair, notwithstanding the dreadful enormity of his death, this is not a case to be met with further imprisonment," the judge said.
Owen, of Morda, near Oswestry, Shropshire, had denied murdering Mr Parkes but admitted manslaughter.
Phillip Shears QC, prosecuting, said the couple had often had violent arguments, and police were called to their home a number of times.
During the argument, Mr Parkes walked on to the knife Owen had picked up after he slapped her about the face. Mr Stephen Williamson QC, for the defence, said Owen still grieved for Mr Parkes, and found it hard to come to terms with her responsibility for his death.Reuse content