Michelle Burger, who lives near Pistorius's home and who had been composed through two days of gruelling cross-examination at the High Court in Pretoria, wept as she finished giving evidence.
Earlier the trial was interrupted and the judge ordered an investigation into allegations that a South African TV channel was broadcasting a photograph of Ms Burger - against a court order guaranteeing privacy to witnesses who request it.
Prosecutor Gerrie Nel asked Ms Burger about her emotions at the time when she made her statement to police. "It was quite raw," she said, her voice breaking.
"When I'm in the shower, I relive her shouts," Ms Burger said of hearing the woman screaming before the sound of gunshots in the pre-dawn hours of Valentine's Day last year. Ms Burger lives about 200 yards from Pistorius's house.
Mr Nel asked her how she was coping. "I'm coping fine," Ms Burger said. "It's been a year."
Ms Burger's testimony about events on the night of February 14, 2013, contradicts the Olympian's story.
Pistorius says he shot four times through a toilet door, hitting his girlfriend Reeva Steenkamp three times in the head, arm and hip or side area after thinking she was a dangerous intruder.
He has pled not guilty to the murder charge lodged by prosecutors, who say Pistorius intentionally killed Ms Steenkamp.
During cross-examination of Ms Burger yesterday, Pistorius's lawyer Barry Roux insisted the university lecturer was mistaken in saying she heard a woman screaming and that she actually had heard Pistorius screaming for help in a high voice after accidentally shooting his girlfriend.
Giving sometimes grisly details of the 29-year-old model's killing, Mr Roux said Ms Steenkamp had been shot in the head, which would have resulted in brain damage and "no cognitive function" and so she would not have been able to scream just after the last bullet struck, as Ms Burger testified.
Mr Roux said: "With the head shot, she (Steenkamp) would have dropped down immediately."
But Ms Burger disagreed, saying: "I heard her voice just after the last shot. It faded away."
Pistorius took notes during the testimony and huddling with lawyers during adjournments.
His collected demeanour contrasted with his sometimes distraught behaviour during a bail hearing last year, when he often sobbed out loud and cried in court. At one point he covered his ears, but it was not clear why.
The only time Pistorius looked anxious was when he prepared to leave the courthouse after the day's proceedings were adjourned.
Surrounded by police officers and private bodyguards, Pistorius ducked his head and walked out as one of the officers said: "Let's go, guys."
Outside, television cameras, photographers and other journalists swarmed around.
The world-famous athlete faces a life sentence with a minimum of 25 years in prison before parole if convicted of murder with premeditation.
Judge Thokozile Masipa earlier warned the media to respect a ruling that images of witnesses who request privacy should not be shown.
TV station eNCA broadcast a live audio feed of Ms Burger's testimony with a photograph of her, prosecutor Mr Nel said in court. He said the photo was captioned: "On the stand: Michelle Burger, Pistorius neighbour."
Judge Masipa said: "I am warning the media, if you do not behave, you are not going to be treated with soft gloves by this court."
Another judge ruled last week that parts of Pistorius' trial could be broadcast on live TV - both in South Africa and around the world - but witnesses who request privacy, like Ms Burger, would not be shown. An audio only feed of their testimony would then be broadcast.
The trial continues.