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SEOUL, South Korea — Polite, petite and soft-spoken, Yeonmi Park has emerged as an unlikely thorn in the side of North Korea's blustering leader, Kim Jong Un.

Park fled North Korea at the age of 13,crossing the partly frozen Yalu River into China in 2007.

North Korean defector Yeonmi Park speaks at the Hong Kong Foreign Correspondents' Club in Hong Kong on April 3, 2017. Vincent Yu / AP file

She says she endured repeated sexual exploitation at the hands of a human trafficker and watched as her mother was sold off and forced to marry a Chinese farmer. Park later trekked across the Gobi Desert to seek refuge in Mongolia before reaching South Korea.

Speaking out has earned her censure in her homeland. Pyongyang has called her a “poisonous mushroom” and a “human rights propaganda puppet.”

Park takes those epithets as compliments. She is glad to have made Kim's regime “feel threatened by my voice.”

Now 24 and living in Chicago with an American husband and a newborn son, Park told NBC News how propaganda infused every school lesson. Kim Jong Il, the father of North Korea's current leader, was regarded as a deity whose portrait hung in every home.

“I thought Kim Jong Il was a god who could read my mind," she said. "I thought his spirit never dies, and I never thought he was a normal human being."

Indoctrination made questioning one's circumstances practically unthinkable, and voicing displeasure with the regime could put one's whole family in danger. “I just never learned to think critically,” she recalled.

But smuggled foreign DVDs like "Titanic" offered a glimpse of life outside of the repressive, poverty-stricken pariah state.

At first, Park struggled to understand how a three-hour movie could be made about a love affair, rather than glorifying a regime.

Her state-run school taught fealty to the government and impressed a hard-line stance toward its enemies, America and Japan.

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Kim Jong Il (left) with youngest son Kim Jong Un (right) as they watch a parade in Pyongyang, North Korea, in 2010. Kyodo via Reuters, file

Park was born in the northern city of Hyesan, near the border with China. Her father trafficked in Chinese-made goods on the black market — clothes, cigarettes, sugar and rice — and later smuggled stolen metals into China. At one point he was arrested and sent to a forced labor camp.

She describes a childhood of occasional comfort but mostly deprivation — extreme cold and hunger at times, and spotty electricity. Days when the lights turned on were so infrequent that they were treated as holidays. Her dream was to have a landline in the house.

In 2007, Park's older sister, Eunmi, who was 16 at the time, escaped to China with the help of a smuggler. Park and her mother made the crossing soon after, hoping to reunite there.

What followed was a harrowing, monthslong journey through a network of human traffickers.

Once across the border in China, Park says that one of the brokers tried to rape her, but her mother offered herself and was raped instead. Eventually her mother was sold as a bride to a Chinese farmer in the countryside.

Park described entering a business arrangement of sorts with her smuggler, who offered to reunite her with her parents if she became his "xiao-xifu," or mistress. The alternative was deportation to North Korea, likely followed by imprisonment or execution.

Park submitted to repeated rape and participated in the smuggling enterprise as a shepherd for other female North Korean defectors.

Before her ordeal, Park assumed that only animals could be bought and sold.

“I lost my faith in humanity," Park said. "I mean I could not trust men again. I hated men. I hated humanity. How on earth can people sell each other?”

Park’s smuggler upheld his side of the bargain. He bought back her mother and smuggled her father into China. Her father died of colon cancer weeks later.

Eventually Park and her mother met another North Korean woman, who told them that South Korea grants refugee status to defectors.

Aided by Christian missionaries operating an “underground railroad,” one night in March 2009, Park and her mother crossed the border between China and Mongolia in the near-freezing Gobi Desert. From there they fled to South Korea.

A map showing North Korea and its neighbors. Bing Maps

Nearly seven years after separating, Park was finally reunited with her sister in South Korea. After years of trauma, her mother is on medication “trying to get better.”

In 2014, she delivered a widely watched speech at a young leaders’ summit in Dublin, Ireland.

Park moved to America to write her memoir and enrolled in the Columbia University School of General Studies, which caters to nontraditional students, focusing on human rights. She is taking a break from her studies after giving birth to a son last week.

Park also advised the Human Rights Foundation on "Disrupt North Korea" initiative. The group's “Flash Drives for Freedom” program sends USBs with Hollywood movies, K-pop and South Korean soap operas into North Korea by balloon.

The group sent 10,000 flash drives in 2016 and estimates that 1.1 million North Koreans have viewed the content.

Park said she believes that the Trump administration's narrow focus on the North's nuclear program has deflected attention from the plight of millions of North Koreans.

Outside information — like the smuggled DVDs that Park once watched — is needed to change people’s minds and ignite grass-roots resistance to the regime, she believes. North Koreans are “thirsty for knowledge," she said.

Park would like to humanize the image of the North Korean people in the foreign media. Too often they are represented as robots, she said, when really they have the “same emotions and same dreams” as everyone else.

Park expects to be able to return to the land of her birth one day. “Nothing is forever, and I believe that North Korea will change in my lifetime.”

Richard Engel reported from Seoul and Chicago, and Kennett Werner from London.