Pretoria, South Africa (CNN) -- Reeva Steenkamp told Oscar Pistorius she was afraid of him and his temper less than three weeks before he shot and killed her, the judge in his murder trial was told Monday.
"I'm scared of you sometimes, of how you snap at me," the South African model told Pistorius in a long chat message.
"You have picked on me incessantly," she wrote, calling Pistorius "nasty" after he apparently accused her of flirting with someone at a party.
"I was not flirting with anyone today and I feel sick that you suggested that," she told him via WhatsApp, according to the police officer who downloaded their chats after Pistorius shot and killed her.
"You do everything to throw tantrums," she said, concluding the message: "I'm certainly very unhappy and sad."
Police Capt. Francois Moller, who downloaded the messages from Steenkamp's iPhone, said that 90% of the chats between the two were normal and loving.
But there were several that accused Pistorius of jealousy and possessiveness.
Less than a week before he killed her, she wrote him another long message after he apparently lost his temper with her as they left a public event together.
She reached the exit before he did, she wrote, adding: "I didn't think you would criticize me for doing that, especially so loudly that others could hear.... I regard myself as a lady and I didn't feel like one after we left."
Pistorius admits that he killed Steenkamp, firing four shots through a closed door in his house in the early hours of February 14, 2013. Three hit her, with the last one probably killing her almost instantly, according to the pathologist who performed the autopsy.
But Pistorius says he thought she was a nighttime intruder in his pitch-black house and believed he was firing in self-defense. He pleaded not guilty to murder.
Moller's testimony came after a neighbor of Pistorius said on the witness stand that she heard "terrified, terrified screaming" the morning the Olympian killed his girlfriend.
Questioned by prosecutor Gerrie Nel, Anette Stipp said she awoke early the morning of February 14, 2013, and heard "terrified, terrified screaming ... It sounds to me as if there's a family murder, why else would she scream like that."
Stipp described hearing a series of three shots, a woman screaming, also a man screaming, and then three more shots before the screaming stopped.
Her husband, Dr. Johan Stipp, testified earlier in the trial.
The trial was originally scheduled to last until March 20 but will now continue until the middle of May, the South African court hearing the case said Sunday.
The trial, which entered its fourth week on Monday, will continue until April 4, then break for a one-week recess before resuming from April 14 until May 16, the Pretoria court announced in a written statement. It said "all parties involved" had agreed to the dates. The trial began March 3.
There has been intense media interest in the case in South Africa and beyond. Pistorius first achieved global fame as an outstanding double amputee sprinter who ran with special prostheses that earned him the nickname "Blade Runner."
Judge Thokozile Masipa will decide the verdict with the help of two lay people called assessors. South Africa does not have jury trials.
In South Africa, premeditated murder carries a mandatory life sentence with a minimum of 25 years. Pistorius also could get five years for each of two unrelated gun indictments and 15 years for a firearms charge he also faces.
If he isn't convicted of premeditated murder, the sprinter could face a lesser charge of culpable homicide, a crime based on negligence.
The sentence for culpable homicide is at the judge's discretion.
Almost the entire trial has been televised, though individual witnesses can choose not to be shown on television.
CNN's Ed Payne and CNN legal analyst Kelly Phelps contributed to this report.