Guilhermina started taking part in local road races with the aim of making money to fund her activities and buy basic foodstuffs.
"The first money that I earned made me believe that I would be able to realize all my dreams," she said.
"I won 80 Reais ($40) in a street race, and stopped in a market to buy a yoghurt that I always dreamed of eating since I was little."
Her ability came to the notice of Brazilian Paralympic officials and she was selected to compete in the 2004 Games in Athens, over the distances of 400, 800 and 1500m.
Categorized as T11 for athletes who have no functional vision, Guilhermina was able to run with a guide, but the athlete nominated to run with her proved of little use.
"When we got to Athens, the first thing he said was, 'You are on your own.' The night before the 400m race, he spent the whole night clubbing and during the event he almost fell ... he was more tired than I was!" she said.
Despite the near mishap, Guilhermina took the bronze medal in the 400m -- but finished down the field in the other two events.
She realized that she was competing in the wrong races, and swapped the two longer ones for sprints over 100m and 200m.
It proved an inspired move and, once she had mastered the skill of driving out of the starting blocks, Guilhermina never looked back.
A world record in the 100m for her category came in 2007 and she won a full set of medals at the Beijing Paralympics the following year.
Her defeat in 100m was a disappointment though, as Chinese runner Wu Chunmiao won gold. "I was slow getting out of the blocks and I stumbled."
But Guilhermina made amends in the 200m to win her first Paralympic gold, and repeated her bronze of Athens in the 400m.
Coming into London 2012, Guilhermina was ever more confident, particularly because of the ability of her guide runner, Guilherme Soares de Santana.
He is her seventh, having come together in 2010.
"He's the best guide in the world because I'm not aware of him on the track. Guilherme has given me back the feeling of running by myself. That's the best gift I could have."
The ultimate goal for 2012 was a hat-trick of Paralympic golds and, after a comfortable win in the 200m, they seemed on track.
Then disaster struck in the 400m, in one of the most heartbreaking moments of the Games.
The pair looked set for victory when Soares de Santana fell in the finishing straight, pulling down Guilhermina in full flight.
The capacity crowd gasped in disbelief as France's Assia El Hannouni crossed the line first while the Brazilian pair lay prone on the track.