[Updated Monday 11:30 a.m.] Afghan police now say that while the woman's throat was slashed, it was not fully cut off - and therefore was not technically a "beheading."

[Updated Thursday 12:16 p.m.] A young woman had her head chopped off for refusing to prostitute herself - and one of the killers was her mother-in-law, police say.

The other was the mother-in-law's cousin. And both admit it, according to Afghan police.

To most people, the slaying of 20-year-old Mah Gul is unimaginable.

But it's just "one more incident that highlights the violent atmosphere that women and girls face in Afghanistan and the region," Suzanne Nossel, executive director of Amnesty International USA, said Thursday.

The killing happened Sunday in Herat province, in southwest Afghanistan along the Iranian border.

Gul's husband is a baker. When he left home for work, his mother and her cousin tried to force the young wife into prostitution, said Noorthan Mikvad, spokesman for Herat police.

When she wouldn't do it, they beheaded her, he said.

In a statement, Nossel said women and girls in the region "are raped, killed, forced into marriage in childhood, prevented from obtaining an education and denied their sexual and reproductive rights. Until basic human rights are guaranteed ... these horrible abuses will continue to be committed."

The U.S. State Department says some "Afghan women and girls are subjected to forced prostitution, forced marriages – including through forced marriages in which husbands force their wives into prostitution, and where they are given by their families to settle debts or disputes."

Some families even knowingly sell their children into forced prostitution, the State Department said, "including for bacha baazi – where wealthy men use groups of young boys for social and sexual entertainment."

Herat police say their investigation found that Gul's husband and father-in-law were not involved in her killing.

CNN has extensively reported on the abuse of girls and women in Afghanistan, a nation where under Taliban rule from 1996 to 2001, women were banned from classrooms, politics or employment. Women who wanted to leave home had to be escorted by a male relative and were forced to wear burqas. Those who disobeyed were publicly beaten. In some parts of Afghanistan in the late 1990s, locals were encouraged to blacken the windows on their homes so women inside could not be seen.

The Afghan government, including a woman running for the presidency of the country, has tried to make it relatively easier for young women to go school. In 2004, girls were formally guaranteed a right to an education under the Afghan constitution.

Yet major problems persist and girls are in extraordinary danger in part of the country. They are terrorized walking to school. In 2009 in Peshawar, Pakistan, near Afghanistan, the Taliban issued an official edict mandating that no more girls should be able to go to school. That was after the Taliban had regained their stake in the control in the region after the 2001 invasion.

Girls and women's families sometimes abuse and kill them. In July, the Taliban executed a woman in public, justifying the killing by saying she had committed adultery.

In 2011, people around the world were appalled to learn about a then-13-year-old named Sahar Gul who had been married off to a member of the Afghan Army. Sahar said her husband raped her, and enraged that she didn't immediately conceive, her in-laws locked her in a basement for months. They tortured Sahar with hot pokers and ripped out her nails. Ultimately, she said, they wanted to force her into prostitution as punishment for failing her obligation as a woman.

Her face made famous on Time's cover, young Aesha had her nose and ears hacked off for running away from her husband's house. Aesha was brought to the United States. Her life continues to be hugely challenging as she's forever emotionally scared by the abuse she suffered.