Tammy Hoggan, who has cerebral palsy, fatally knifed Leslie Carrington at a flat in Kirkcaldy, Fife in December 2013.
Mr Carrington, 48, had spent the hours before he was attacked watching University Challenge and listening to music with friends.
Hoggan, 29, denied murder during a trial at the High Court in Glasgow.
But a jury heard she told five different police officers she had attacked Mr Carrington. Hoggan, who wept after being found guilty, now faces a life sentence when she returns to the dock next month.
The trial heard how the victim had been with friends Douglas Butters and Hoggan’s ex, Robert Lawson, before he was killed.
Mr Butters, 46, told how they had been at his flat on 16 December 2013 watching TV and listening to music.
The witness recalled: “We were absolutely delighted that we had got three questions right on University Challenge. It was jovial; we were all quite smart, articulate people who liked to fire off with stimulating conversations.”
Mr Butters then told how Mr Lawson was later bombarded with calls from his former lover Hoggan. He eventually went to his flat with Mr Carrington before Hoggan also showed up.
Mr Lawson recalled Hoggan being “distraught” as she had apparently had a row with her mother.
The witness then told how his ex later kicked over a table before he realised she was clutching a knife as she sat beside Mr Carrington.
Hoggan, who has problems down her right side, had the blade in her left hand. The court heard she made a stabbing motion towards Mr Carrington three times.
Mr Lawson said: “I saw Les leaning forward then the blood running between his legs on to the couch then on to the floor.”
He also remembered the victim saying: “Tammy, I can’t believe you stabbed me.” Mr Carrington never recovered from his injuries. The jury was told that Hoggan later made a string of admissions to several police officers.
She told one: “I stabbed him, his eyes were rolling back in his head. How can I sleep now after what I done?” Hoggan confessed to another: “I can’t get over what I done. I stabbed my pal through the heart.”
The court also heard the killer describe her victim as a “lovely guy, harmless and caring”. But during the trial, Hoggan denied murder, insisting: “I believe that I did not do that. I know that’s not me.”
She also claimed she remembered very little of the incident and said it was her ex, Mr Lawson, who had told her she was responsible.
But prosecutor Bruce Erroch, in his speech to the jury, described this as “an attempt to rewrite history”. He added: “The evidence of Tammy Hoggan does not wash. She is trying to pull the wool over your eyes.”
Sentencing was deferred for reports.
SCOTSMAN TABLET AND MOBILE APPS