When Springbok Andre Esterhuizen fouled fellow centre Jose Lima with less than three minutes on the clock, she watched replays of the incident and flashed a yellow card in the one-off Test.
She also told an off-field official to review the incident and decide whether the punishment should be upgraded to a red card. Several minutes later yellow turned to red.
Davidson once again lifted a card from her pocket on 35 minutes for foul play with South Africa winger Kurt-Lee Arendse the offender.
This time she was satisfied 10 minutes in the sin bin would suffice and a relieved Arendse returned in the second half after the Springboks were temporarily reduced to 13 men.
The Scot took further disciplinary action five minutes from time with substitute Quan Horn yellow-carded after a foul.
Assistant coach Mzwandile Stick had hailed Davidson before the match.
"Hollie always displays confidence and I like the way she handles matches. Congratulations to her on becoming the first woman to handle a Springboks Test," he said.
"Well done to World Rugby too for making this appointment. This is what transformation in rugby is all about.
"I have no doubt we will see a lot more women referees rising through the structures and handling Tests in future."
"Before our match against Portugal, I had watched Hollie many times in the United Rugby Championship and she handled every match capably.
"Her appointment to handle the Springboks for the first time was thoroughly deserved."
