The younger Pistorius made history when he became the first Paralympian to compete in the able-bodied Olympics last year. He ran on special carbon fiber blades affixed to his legs. He was born without the fibulae in his legs, and they were amputated below the knee when he was 11 months old.
Before she died, Steenkamp sent out a message urging her thousands of social media followers to empower women.
"Speak out against the rape of individuals" in South Africa, she said in a post on the photo-sharing site Instagram. "RIP Anene Booysen."
Booysen, 17, was raped and mutilated in South Africa this month, putting a spotlight on violence against women in the nation.
Steenkamp urged her followers on Twitter to wear black the day after Valentine's to protest violence against women.
A tragic end on Valentine's
Steenkamp was looking forward to Valentine's Day.
"What do you have up your sleeve for your love tomorrow?" she asked her Twitter followers the day before. "Get excited."
At dawn, she lay dead in a pool of blood.