Unmarried and child-free, when Drolma, 45, drives herself around the chaotic capital of Kathmandu in her saffron robes honking her horn as her songs blast from the radio, she is defying just about every expectation of women in Nepal.

"I have been the most revolutionary person I can think of in my society," Drolma tells CNN.

She isn't exaggerating.

Tough beginnings

Drolma's father did hit her.

"Small things irritated him and he'd beat me and my mum," she says. "Today, I see it as a disease he was suffering from. But in those days we all suffered because of it."

Aged 10, full of anger and fear, Drolma resolved to become a Buddhist nun -- in Nepal, nuns are not permitted to marry or have children.

"I thought, 'If I grow up and get married that man will treat me the same way'. Domestic violence is a big problem in our society."

Her parents were approving of Drolma's decision -- "our cultural belief is that when someone becomes a nun they are going to live their life more positively" -- and three years later she was accepted by a local monastery.

Without hesitation, Drolma shed her hair, everyday clothing and birth name, Dolma Tsekyid.

"When I first got (my head) shaved I felt so free, I could feel the breeze."

Nagi Gompa monastery was located on a mountaintop in the Kathmandu Valley, and to Drolma it was "paradise".

"The whole environment there was beautiful. Everyone was kind, and I never got beaten, or had to carry my two younger brothers on my back. Or do the cleaning.

"I was given my childhood back."

Outside influence

Foreigners would often visit Nagi Gompa seeking spiritual enlightenment.

In 1993, American record producer Steve Tibbetts turned up at the hilltop retreat with his wife to learn meditation under Tulku Urgyen, who he described as "a great meditation master" and Drolma's main teacher.

On their last night, a translator at the monastery asked Tibbetts to record Drolma, then aged 22, singing.

"She sort of rolled her eyes -- 'Who is this guy with his cassette recorder?' -- took a deep breath, and sang some lines from 'Leymon Tendrel.' I was amazed, dumbfounded," Tibbetts says.

So dumfounded, in fact, that Tibbetts forgot to press "record".

"There's a quality in her singing that cuts to the heart of what it's like to be human," he says. "That quality, that tonality, just goes right to the center of your chest."

Tibbetts returned a few days later and captured Drolma's voice. On returning to the US, he set her haunting Buddhist hymns to a guitar track, and sent the recording to Nepal, suggesting the pair collaborate on an album.

"Without calculation, I just did it," Drolma says, "and later on it created some kind of a miracle in my life."

While Drolma attributes her big break to Tibbetts, he is adamant the opposite is true.

"Just to be clear, she wouldn't be denied," he tells CNN, via email from the United States. "If I hadn't have met her and started her off, she would have found someone else."

The singing nun

The first album was called "Cho".

The vocals were recorded at the nunnery in Nepal, and Tibbetts brought on board the legendary American hit maker Joe Boyd, who has worked with Pink Floyd, Nick Drake and Billy Bragg, to produce the album.

"Cho" sold well -- although Drolma refuses to disclose the figures; "I don't think about numbers" -- and a U.S. tour was planned.

"I had two other nuns on stage with me, along with Steve and a guy on sound. We had a huge bus and we toured," she remembers. "In New York we played (Brooklyn venue) the Knitting Factory. The fans were all Americans, there wasn't a Nepali face in sight."

Along with fast food, American women were a culture shock.

"I was surprised by the independence and confidence the women there carried," she says. "They all drove. They were educated. I was inspired."

Back in Nepal, Drolma bought a computer, installed an internet connection at the monastery, and opened a bank account.

More money, less problems

The financial resources from the tour gave Drolma the chance to realize her dreams.

In 1998, she founded the Nuns' Welfare Foundation (NWF).

Unlike at the monastery where Drolma grew up, in addition to religious teachings, the girls receive lessons in English, Nepali, mathematics, science, and computing -- subjects to prepare them for careers. Many have gone on to higher education.

"Some of the nuns later quit being nuns," she explains. "At that point, a secular education helps them survive a modern life."

"I remember (receiving) a letter from Ani after our first tour," says Tibbetts. "She said she'd realized that there was a chance to make some real money on the road and fulfill her dream of creating a school for young girls in difficult circumstances. She told me she wanted to do more tours."

In reality, Tibbetts thought "she was probably more interested in getting a jeep, or a flat somewhere in Kathmandu."

He was wrong. She did exactly "what she said she was going to do", he remembers, and she "smashed through a lot of barriers in the process: religious, cultural, patriarchal".

"I'm the first nun in Nepal sending children in nuns robes into normal colleges," Drolma tells CNN. "They've never had that type of encouragement before."

Fame and fortune

Over the next decade, Drolma made nearly an album a year: in 2002, her and Tibbetts even recorded in a cave believed to have once been home to 8th century Buddhist guru Padmasambhava.

She has performed around the world -- including to an audience of 20,000 people in Tibet last Easter -- counts superstars like Tina Turner and Tracy Chapman among her fans, and her biography "Singing For Freedom", first published in French in 2008, has been translated into 15 languages.

Drolma has used her position to benefit those less fortunate than herself.

In 2010, the NWF opened the Aarogya Foundation, which provides medical services to those with kidney problems and has successfully lobbied the government to provide free dialysis to poor people in Nepal.

"I lost my mother to kidney disease," Drolma says. "When she was suffering I took her to India twice, but I still couldn't keep her alive."

Brave nun

In 2011, Drolma showed her willingness to challenge the establishment when she offered sanctuary to a 21-year-old nun who had reportedly been gang raped and ostracized from her religious community.

"She is a human being like everybody else. This could have happened to anybody," Drolma said at the time.

"It could have happened to me, to my sister. The most important thing is to treat her like a human being and then later we can look into the matter of whether she is still a nun."

If Drolma risked being ostracized by speaking out she didn't seem to care.

She had long been criticized in conservative Nepal for appearing in liberal Western magazines like "Marie Claire", her love of Hindi films and her global pop career -- all deemed inappropriate for a nun.

"As a nun," Drolma says, "I'm supposed to be living in a very limited way. Nuns are not supposed to do this, to go there, to say that. They even think a nun should not sing.

"Yet I am someone who has come out and done everything to shock people."

She pauses, and moderates her comments slightly: "I mean, I never sing tragic love songs, they are all meaningful spiritual hymns."

In a patriarchal country, Drolma is unique in having achieved total independence. In Kathmandu she lives in her own flat, drives her own car, and has a successful career.

"I have never regretted my decision to become a nun," she says, with confidence. "Yes, I missed out on the complicated married life. But some married women seem to regret not being able to go here or say this.

"For me, I'm completely enjoying my freedom. In fact, I am grateful for my childhood, even for my father.

"It has all been a blessing in disguise."