(CNN)Zaynub Afinnih lives thousands of miles away from Sudan, but the story of a 19-year-old woman who was sentenced to death there for killing her rapist inspired her to start a global campaign calling for justice.
"I don't know her ... I've never spoken to her," the 16-year-old activist told CNN from her family's home in Rouen, France. "But she is my sister in humanity. I can't let her die for defending herself against the man who raped her."
Noura Hussein was imprisoned in Omdurman, Sudan, last year after fatally stabbing the man she was forced to marry, who she says raped her as his relatives held her down.
The harrowing details of her case have set social media ablaze and captured international attention with the hashtags #JusticeforNoura and #SaveNoura.
Afinnih first came across Hussein's story on Instagram, and then read more about her in a blog post. She said she was shocked by the story.
An illustration used in the change.org campaign for Noura Hussein.
"It was just horrific. I couldn't read the story and go back about my normal day," Hussein said. "After that I made the petition. I felt like I had to do something."
From the ground-floor flat she shares with her Nigerian mother, two sisters, and brother, Afinnih decided to create a change.org petition appealing to the Sudanese government to save Hussein's life.
Teen to die for killing husband she says raped her 01:24
The petition has gone viral, garnering more than 700,000 signatures so far.
After starting the petition from the bunk bed of her bedroom, Afinnih shared it with her followers on Instagram and Twitter, calling on her friends to do the same.
"She's a hero," Afinnih said of Hussein. "She's representing all the women who have been oppressed in their lives."
Hussein's family compelled her to marry at 15 -- one year younger than Afinnih -- but she refused and ran away for three years. Her father forced her to complete the wedding ceremony last April. After refusing to have sex with her husband on their "honeymoon," she says he raped her as his brother and two cousins restrained her.
Calls for mercy mount
Noura Hussein on her wedding night.
Since Hussein was sentenced on May 10, calls for mercy have mounted internationally.
UN Secretary-General Antonio Guterres demanded Sudan stop any attempt to execute Hussein, and urged respect for her claim of self defense against attempted rape.
Saying that Guterres was following the case closely, UN deputy spokesman Farhan Haq told CNN that the UN "calls for halting any steps being taken toward her execution, which, on the basis of the information made available to us, would violate international human rights law and standards, thus constituting an arbitrary execution."
Amnesty International has collected 174,000 letters from people around the world asking for her release -- they've sent 150,000 of those letters to Sudan's Ministry of Justice, Amnesty International's Deputy Regional Director for East Africa Seif Magango told CNN on Thursday.
Amnesty is waiting for a response, he adds.
"What we ask the international community is to stand with us to free Noura," he said. "She doesn't deserve to die for defending herself."
A representative from the US State Department told CNN it "echo(es) the statements of many in the international community and within Sudan, condemning early and forced marriage and violence against women and girls."
"We have raised this case with the government of Sudan, and note that it is still going through a judicial process; we look forward to an appropriate resolution of her case, consistent with Sudan's international human rights obligations."
The Sudanese government has not responded to CNN requests for comment on the case.
