Reeva Steenkamp's mother June believes that "trigger-happy" Oscar Pistorius "would have killed someone sooner or later".
The six-time Paralympic champion was sentenced to five years in prison after being found guilty of culpable homicide.
The 27-year-old claimed that he mistook Steenkamp for an intruder when he fired four gunshots through a toilet door at his home in Pretoria, South Africa in the early hours of Valentine's Day last year.
June Steenkamp told The Times, who are serialising her book Reeva: A Mother's Story, that her daughter had "nagging doubts about their compatibility" and considered leaving him.
"She had confided to me that she hadn't slept with him," said June. "They'd shared a bed, but she was scared to take the relationship to that level.
"She wouldn't want to sleep with Oscar if she wasn't sure. I believe their relationship was coming to an end. In her heart of hearts, she didn't think it was making either of them happy."
June added: "Her clothes were packed. There is no doubt in our minds: she had decided to leave Oscar that night."
Reports have claimed that Pistorius will spend 10 months in jail before serving the rest of his sentence under house arrest.
Danielle Joynson
