"It would be like asking someone who cannot swim to save another swimmer," Tsang said, adding that it was hard for someone on the ground to imagine the challenges facing climbers at an altitude above 8000 metres.
None of the hikers with her stopped and offered the man help, Tsang said.
The man was dead when they came back downhill.
Tsang arrived back in Hong Kong after her expedition up the world's tallest mountain on Sunday. She has since faced criticism from some internet users for what they see as disregard for other climbers' suffering.
One Facebook user, posting a comment on a news story about Tsang's achievement, wrote: "Seeing a man like this, any conscientious person would immediately give up conquering the peak and save others first."
Another asked: "How could she justify the behaviour of leaving others to die for her own glory?"
Tsang said the image of the dying man haunted her. But when she discussed it with her Sherpa guide later, she said, the experienced mountaineer told her the man was doomed to die by that point, as he had suffered serious frostbite, and an oxygen bottle would not have saved him.
"I guess it was his own choice," Tsang said. "Hikers aiming to conquer Mount Everest make light of death."
The Hong Kong teacher revealed earlier that she had passed four dead bodies and overtaken 40 to 50 climbers in No 8 typhoon-level winds on her way to the peak.
Tsang also narrowly escaped death on her previous attempts.
In 2015, she fractured her skull after being caught in an avalanche triggered by a 7.9-magnitude earthquake that killed 17 climbers.
- South China Morning Post