Hours earlier, she had received a phone call from fellow activist Sharaf, who urged her to come and meet him.
As soon as she stepped outside, however, she realised it was a trick.
Ms Al Sheikh saw her friend being held at gunpoint, but before she could react, they were both bundled into the back of a white Toyota with no licence plates.
After a terrifying ordeal that left her barely able to speak about her experiences, Ms Al Sheikh was dumped outside her house in the early hours of March 28.
Sharaf, a 19-year-old student at Sudan's University of Science and Technology, is still missing.
Families and lawyers of those caught up in a spate of kidnappings say Sudan’s security forces are behind the abductions of young activists protesting against last year’s military takeover.
The Sudanese capital Khartoum has been the scene of many enforced disappearances, with human rights lawyers and activists saying that at least 43 people have been abducted over the past four months.
The victims, many of whom are still missing, were taken by armed men who presented neither identification nor arrest warrants and drove vehicles with no licence plates.
Witnesses to these incidents, as well as the families and friends of some of those who have disappeared, told The National that Sudan's security services were kidnapping protesters as young as 18 in Khartoum and Omdurman in a new tactic designed to stifle dissent and silence critics of the military.
Repeated requests by The National for comment on the claims from the Interior Ministry, a general in the army and a former officer close to the new ruling Sovereign Council were not returned.
Sudan’s Interior Ministry has denied its involvement. In recent statements to local media, it has accused what it described as a ‘third party’ of being behind the abductions of activists.
Officials claim that “anarchists, outlaws and ex-convicts” are exploiting the current unrest as fully as possible.
The ministry further says that some of the protesters are involved in violent riots that have erupted in recent weeks in Khartoum.
‘We hold the military authorities accountable’
The family of Ms Al Sheikh have no doubt as to who is behind her abduction and say she has been shaken by the incident.
“She’s traumatised and in a miserable condition,” her aunt, Nagla Sid Ahmed, told The National.
“We hold the military authorities accountable for her kidnapping and enforced disappearance for several days without knowing whether she was dead or alive. We haven’t slept since then and searched for her in every detention centre and police station in Omdurman and Khartoum — to no avail.”
Sharaf -- Yasmin's friend -- was detained by unidentified armed men during an anti-coup protest at Al Sahafa neighbourhood in Khartoum in early March, according to family and friends.
“Yasmin is just like thousands and millions of Sudanese men and women who want a civilian government and democracy. She isn’t affiliated with any political party. She just posts anti-coup statements on her Facebook and is among dozens of activists who have been kidnapped by the government’s forces,” Ms Ahmed said.
Human rights groups define enforced disappearance as arbitrary detention lasting a few days or more.
It is unlike an ordinary arrest because the state refuses to release any information about the person’s whereabouts.
‘No one is safe’
Two weeks ago, Jad Abdullah, a 19-year-old university student, was bundled into a black sedan by armed men, his close friend Abu Bakr Fathallah said.
“They are afraid of expected mass protests on April 6 to mark the third anniversary of the sit-in at the army headquarters in Khartoum, which forced [former autocrat Omar] Al Bashir to stand down a few days later,” said Mr Fathallah, who studies at the Korean Technical Institute in Khartoum.
“No one is safe. They have killed many people so far and kidnapped dozens to silence us,” he told The National.
Since the coup on October 25, thousands of people have been rallying in Khartoum and its twin city of Omdurman, demanding Sudan’s generals hand power back to civilians.
Authorities have launched a deadly crackdown, firing live ammunition and tear gas at the protesters, says the Professionals Association and the Forces for Freedom and Change, an alliance of political parties and groups that spearheaded the uprising that resulted in the removal of Al Bashir from power in 2019.
The UN human rights office in January condemned what it said was the brutal, disproportionate use of force by Sudan’s security forces against protesters.
The country’s military rulers, it said, should investigate allegations of human rights violations, including killings, forced disappearances and incidents of sexual violence against women.
About 90 people, including 15 children, have been killed since the military take over, says the Sudan Doctors Committee, which tracks casualties among protesters.
'We will keep up the pressure'
Last week, the body of journalist and pro-democracy activist Azzam Al Hibr Nour Al Daem turned up on the banks of the river in Khartoum a few days after he had disappeared.
Authorities say they have opened an investigation into his death.
Khalid Bekheit, a lawyer for pro-democracy protesters and a long-time human rights activist, said Al Daem’s case had been registered as an enforced disappearance by his network of Emergency Lawyers in Khartoum.
“We found the body of Azzam one week after his disappearance. We have documented cases of activists who were found dead and their bodies carried signs of torture. We are also aware of others who have been released after weeks of secret detention and developed serious mental health conditions including trauma, depression and suicidal tendencies.”
Once a disappearance is reported to his network of rights activists and lawyers, Mr Bekheit says his team begins searching for the missing person by scouring the city’s police stations before reaching out to the Interior Ministry.
But the authorities, he says, do not co-operate.
“In all 43 cases we have documented so far since last year’s coup, we have been unable to get any word from officials, who always deny that the security forces are behind the enforced disappearances. They often blame armed groups and gangs for it.”
Mr Bekheit says secret detentions are playing an important role in a broader effort to stamp out dissent.
Under Al Bashir, he says, the security forces rarely went after young activists, instead focusing their attention on the most vocal opponents of the regime.
Despite the crackdown, Mr Bekheit vowed to keep working to protect the rights of protesters.
“All these people who go missing nowadays have two things in common: they are young and anti-coup,” he said. “We will keep the pressure and publicise their case until we find them.”