The intimate images show the Steenkamp as a law student – before her modelling career took off.
They were captured by her close friend Kerry Smith, 37, who attended university with Reeva in Port Elizabeth, South Africa, where they both grew up.
Reeva Steenkamp as pictured by her friend Kerry Smith when the two were law students
The images are a "bittersweet reminder" of Steenkamp for Smith, who spoke at her funeral on February 19, 2013.
She said: “When the judge delivered a “not guilty” verdict [for murder] - I was horrified.
“I had to drive to my son’s school for a sports game after hearing it - when I turned off the TV, I left to the school totally disillusioned with the outcome and for the first time since the trial started, I broke down.
“I still have no closure of her death - in my mind Reeva is still so vibrant and alive. I miss Reeva. I really, really miss her.”
Smith photographed Steenkamp on a South African beach
Smith and Steenkamp were close friends in school, but the two grew apart after graduation in 2005 over of a clash of opinions about Smith partner at the time.
Smith said: "I was in an unhappy relationship. Reeva didn’t like my partner and couldn’t understand why I was with him, so we stopped talking.
"She contacted me in 2007, after she found out that I had left him. She said it was her dream come true and she was glad I found happiness."
Smith met Steenkamp at the University of Port Elizabeth in 2002, where they both studied law.
"We were all asked to break off into groups for a project, and Reeva was in my group,” said Smith.
"We lived just up the block from each other, and we rode into school together in the morning. It blossomed from there, and we became the closest of friends."
Smith, an aspiring photographer, tested her camera skills using Steenkamp as her subject - and the result was this beautiful set of photos of the then-aspiring model.
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One set of photos shot by Smith show Steenkamp, then 19, posing at Sardinia Bay in Port Elizabeth.
Smith said: "If there was ever any proof anyone needed to show that Reeva was truly a natural beauty, this is it.
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"She did not have a stitch of make-up on and we didn't do anything fancy with her hair.
“She told me she wanted to go back into the modelling industry, but was hesitant because she wanted to have a stable career.
Pistorius and Steenkamp in November 2012, three months before her death
“She said ‘modeling can't be forever because we get older, beauty fades, wrinkles appear’."
Despite her doubts, Smith had managed to convince her to go to the beach for a few shots.
She added: “She was shy and self-conscious at first, but eventually grew comfortable in front of the camera.
“Reeva was always the down-to-earth girl next door - you can see that the first few photos are of her in a black polar neck sweater with no flesh showing, and later with a bare midriff.
"The whole process was drowned out in fits of laughter while we we tried to be professional and serious."
Other photos taken by Smith show Steenkamp sporting pyjamas and drinking coffee with uni pals at a sleepover.
Smith said: "She had this really loud laugh, it wasn't cute and giggly - it was one of those laughs that made everyone laugh too."
Smith said Steenkamp and she were passionate about issues like domestic violence and discussed plans to one day open up a clinic for women who were in abusive relationships.
"Reeva wouldn't back down from things that she stood against,” she said.
Steenkamp's mother June arrives in court for the sentencing on Tuesday
“She wouldn't keep quiet, and didn't change at all even when she was in the model business.”
On February 14, 2013, Pistorius was arrested for questioning after shooting and killing Steenkamp at his home in Pretoria, South Africa.
He was formally charged with murder the next day - but claimed he shot Steenkamp thinking she was an intruder.
Smith: "Looking at these pictures, seeing Reeva laughing - going from that and then having to speak in front of her coffin, it's surreal. You just can't wrap your head around it.”
As Pistorius’s trial began, Smith was painfully reminded of Steenkamp’s tragic death.
Kerry said: “I was riveted at the outset of the trial and despite my personal connection to the matter I tried to keep an unbiased view when listening to the evidence being read.
“The only time I broke down was when I saw the head shot of Reeva which showed her wounds.
“I remember wondering ‘why is her hair black?’ and then I realised it was all the blood."
Pistorius pleaded not guilty on March 3, 2014, but on September 12 he was found guilty of culpable homicide.