The 19-year-old top student, a teacher's daughter in a small village in the poor southern province of Minya, dreams of becoming a doctor like her two brothers.
In previous years she aced her exams, and had expected a similar result in her final year.
Now nicknamed the "zero schoolgirl" in the local press, Malak had scored 97 percent in her previous two years.
But Malak was shocked to find that she had been failed in her finals, and says her answers had been replaced with someone else's -- clearly not in her handwriting.
"Since the results came out I've been living a nightmare," Malak told AFP after coming to Cairo from her home in southern Egypt.
"When I was shown the so-called copy of my answers, I couldn't believe my eyes," she said.
Malak said she had written page after page in the exams, and what she was shown consisted of a few lines.
In highly bureaucratic Egypt with its confusing legal system, challenging rampant corruption or wrongs suffered by the average citizen can be a formidable task.
- Were her papers swapped? -
But Malak, who wears thick glasses and has her hair in a simple ponytail, is standing up for her rights and challenging the exam results.
Her lawyers believe Malak's exam papers could have been swapped with those submitted by the child of a person of influence.
When the final result first came out, a disbelieving Malak appealed to the education authority in the southern city of Assiut, which dismissed the complaint.
So she appealed to the prosecution service, which tasked a forensics team in Assiut to determine if the answers were in her handwriting.
Signup to our newsletter and follow us on Facebook and Twitter!
Malak was again stunned when the experts ruled that the answers were indeed in her handwriting, and the prosecution closed the case.
So she again appealed against the decision.
"When she first heard of the forensic report she fainted," said her brother Mina, a doctor in his thirties who accompanied his sister to Cairo.
Malak was hospitalised briefly, and then appeared in tears on a television show, a catheter for a drip still inserted in her hand.
"I know I'm fighting corruption because the way my results were announced and forged means that corruption exists," she said.
- 'I believe Mariam Malak' -
By the time Malak lodged her second appeal, her story had become a mainstay of television talk shows and in the newspapers, with people taking to Twitter with the hashtag "I believe Mariam Malak".
Her case finally came to the attention of Prime Minister Ibrahim Mahlab, who invited Malak to the capital for a meeting and issued a statement backing her.
Mahlab said he would "support the student in her appeal as if she were his daughter".
The Coptic Pope Tawadros II also asked to meet her, but Malak, a Christian, declined lest it appear a sectarian issue, saying her case was "that of an Egyptian citizen".
The prosecution service has now reopened the case, this time appointing a forensics team in the capital to study the handwriting in the answers attributed to her.
Malak's case has seized the public imagination as Egypt reels from a corruption scandal that led this week to the arrest of the agriculture minister immediately after he was told to quit.
There are also rumours in the press of a pending cabinet reshuffle.
At the education ministry, a senior official insisted that justice would be upheld in Malak's case.
"We are not with anyone or against anyone, and we respect justice," said Mohamed Saad, adding that the prosecution findings would be implemented.
"If you respect my rights in my country, all those who live in injustice will know they can claim theirs as well," Malak told AFP.