Pistorius, a double-amputee Olympic sprinter, was convicted of culpable homicide on September 12 for which he received a maximum prison sentence of five years, with the possibility of serving the rest under correctional supervision after 10 months.
Steenkamp said about sitting near him in the trial: "That was scary. Because he was the one who killed her, and he hurt her and he terrorised her.
"We all love our children and we adored Reeva. And to sit next to the person who killed her - and she didn't do anything and she had no protection - horrible."
Pistorius, 28, pleaded not guilty to murder and said that he mistook Reeva for an intruder in his bathroom before he shot four times through the door, with three bullets hitting his girlfriend.
Steenkamp, whose book Reeva: A Mother's Story is out in the UK, also said that her only child Reeva kept quiet about their relationship at the beginning as "she wasn't sure if they were compatible" and she told her mother that she could not understand why they were fighting so early on.
She said: "She didn't tell me about Oscar - the first time I saw them together was on the red carpet at a sports award. And I thought: "Now, who is this man?" Because I'd never heard of him."
Reeva moved from her parents' home in Port Elizabeth aged 22 to the bigger and more dangerous South African city of Johannesburg to continue a successful career in modelling - which she had done since the age of 14 - after graduating with a law degree and working as a paralegal.
Also a reality television star, Reeva was due to be shown in Tropika Island of Treasure two days after she was shot by Pistorius. Her parents gave SABC 1 permission to air the show.
Steenkamp said: "I said I would just love to see her alive, happy and laughing. Lots of people couldn't understand that but to me it was like bringing her back, seeing her laughing and enjoying herself."
- The Independent