Racing at Pilditch Stadium in Tshwane, Marais clocked 11.51 seconds to secure her first USSA title since 2021, marking a triumphant comeback.
She edged out North West University's Chardone Smidt, who took silver in 11.59, while Annestaysha George of the University of Pretoria claimed bronze in 11.68.
Defending champion Joviale Mbisha, a two-time USSA 100m winner and newly crowned national senior champion, had a disappointing outing, finishing eighth in 14.59 seconds.
"I'm extremely grateful to God for watching over me during the race. My body hasn't been feeling the best, so I'm just extremely grateful for everything," said a joyful Marais.
The 21-year-old, currently in her fourth year of law studies at Kovsies, was in disbelief after winning a race that included South African senior 100m champion and USSA titleholder Joviale Mbisha, an athlete she deeply respects and admires in the local sprinting scene.
"Joviale is such a fierce competitor, and I have so much respect for her. I also love racing against her because she brings the best out of you.
'It was definitely not an easy race, both mentally and physically, and I was very fortunate to win on the day," said the humble Marais.
The sprinter, coached by the legendary Tannie Ans at Kovsies, the same coach who guided Wayde van Niekerk to his historic 43.03-second Olympic and world record in 2016, told the national broadcaster that her confidence grew with each round, and by the final, she fully believed in herself.
The Bloemfontein-based sprinter says she is gaining valuable knowledge from 75-year-old coach Tannie Ans, who has developed some of the country’s top sprinters and remains passionate about mentoring the next generation during training sessions at Kovsies.
Marais is aiming to earn a spot on Team South Africa for the World University Games in Germany, scheduled from 13 to 27 July, and is also planning to compete in several league meetings across Europe.