Reeva Steenkamp sent a text to her flatmate on the night she was shot dead, saying she would not be driving home because it was "too late".
Gina Myers, who shared a home with Miss Steenkamp in Johannesburg, told Sky News' Alex Crawford that the text was the last message she received from her friend.
Miss Myers said she had met Oscar Pistorius, who is accused of murdering his 29-year-old girlfriend at his luxury home in Pretoria, a few times and did not know him well, but had liked him.
She said Miss Steenkamp had been happy with the gold medal-winning Paralympian and would not have been with him otherwise.
She told Sky News: "It was like any other relationship. There was nothing that flashed a warning sign. She was happy. She was very happy.
"Reeva was not the kind of person to complain about stuff, but she would never have been with anyone if she wasn't happy. Her motto this year was to 'be happy and never settle'."
Miss Myers was speaking as it emerged that Pistorius held a private memorial service for Miss Steenkamp at his uncle's house in Pretoria.
The South African athlete has been staying at his uncle Arnold's house since being released on bail last Friday after being charged with the model's murder.
The 26-year-old, who also competed in the Olympics last summer, denies murder and claims he shot Miss Steenkamp by mistake believing she was an intruder.
Miss Steenkamp's funeral was held in Port Elizabeth last week, as her boyfriend appeared in court and insisted her death was an accident.
He has to abide by strict conditions while he is on bail, including reporting to a police station in Pretoria twice a week.
The athlete was also ordered to surrender his two passports, post bail of one million rand (£75,000) in cash and guarantees, and refrain from drinking alcohol.
Pistorius was also ordered to hand in any guns he owns and keep away from his home in a gated community in Pretoria, which is now a crime scene.
Prison service officials can drop in at his uncle's house at any time of day or night to ensure the athlete is complying with the bail terms.
Pistorius, who had his lower legs amputated at the age of 11 months after he was born without either fibula, rose to global fame with his fight to be allowed to run in the Olympics against able-bodied athletes.
He reached the semi-finals of the 400 metres at last year's London Games.
His case resumes on June 4.