A woman has been jailed for life after stabbing her mother's best friend in an "act of gratuitous violence".
Cardiff Crown Court heard Rebecca Press was high on drugs and alcohol when she attacked Richard Marc Ash in New Tredegar in July last year.
The court heard Press left Mr Ash, 57, who was described as a "gentle soul" dying on the floor and ran from the flat where she then called her ex-boyfriend admitting, "I've just stabbed someone and killed them. I've just murdered someone. Please phone me now. I've just murdered someone".
Press had taken Valium earlier that day before going out drinking with Marc Ash.
CCTV shows Press heading to the pub with Mr Ash in high spirits singing and dancing.
She returned to her mother’s home and became increasingly upset and assaulted her mother, the court heard.
Body worn footage from police shows her brother explaining to officers that Mr Ash tried to calm her down but she stabbed him once to the chest.
In the call to police, which was played to the jury, Mr Ash said: “It’s all kicking off here at the moment.
“I’m in my neighbour’s house.
“There are two people who are not wanted in here and they have assaulted people.”
The injury led Mr Ash to suffer a cardiac arrest from loss of blood and die.
When she was eventually spotted by police and arrested on suspicion of murder she “feigned surprise”, asking officers: “Have I murdered someone?”
A healthcare professional who examined Press at the police station commented how she was shocked at how “oddly calm and jovial” she was.
The next day tests revealed Press had benzodiazepines in her system as well as MDMA, also known as ecstasy, and traces of THC a chemical found in cannabis.
She told detectives she had "no intention" of killing him and was "acting in self defence" claiming she was in fear of her safety.
On the fifth day of a crown court trial, she changed her plea to guilty of murder.
Mr Ash's family described him as a "gentle soul" who was "intelligent, kind, gentle and funny."
His daughter said, "I hope to study Law as a career and my father will never see me go to university, graduate, or start a family. He didn’t see me reach my 18th birthday, pass my driving test or exams of which I know he would be proud.
"All these opportunities I have been denied and will have to live with the fact that I no longer have a father for the rest of my life."
Millie Davies of the CPS said: “Rebecca Press killed Marc Ash, her mother’s neighbour and best friend, in a senseless act of gratuitous violence whilst under the influence of drink and drugs.
“During the course of the evidence being presented to the jury by the CPS, Press decided to change her plea, pleading guilty to murder.
“Marc Ash was simply trying to help a friend in distress, a decision which tragically cost him his life. Our thoughts remain with his family and friends.”
The judge said it was clear Ms Press caused "terrible grief" to Mr Ash's family.
She said although the murder was not planned, it was "spontaneous".
No credit would be given for her guilty plea and she waited to until her brother had given evidence to the jury.
The court heard Press had 16 previous offences for violence.
Rebecca Press was sentenced to serve at least 20 years behind bars before being considered for parole.