Kerri-Lisa McCammont, 18, was told by Mr Justice Latham that the sentence was the least he could impose, and her greatest punishment would be living with the terrible thing she had done.
McCammont, of Crawley, West Sussex, was convicted at Lewes Crown Court in October of killing Joanne Thorns, 18.
The court was told she went to apologise to Miss Thorns because she felt guilty about taking her boyfriend. It was accepted that she had no intention of doing her harm, but Miss Thorns struck her and a fight began in which she suffered fatal knife wounds.
The hearing at Lewes was adjourned for medical reports. The judge at the High Court in London yesterday was told that McCammont had a psychopathic disorder which required treatment, but no hospital place was available.Reuse content