An Emirati princess who disappeared after witnesses described her being seized by commandos on a yacht had spent seven years planning her failed escape bid from the Gulf state she considered a gilded prison, according to her friends.

Sheikha Latifa bint Mohammed al-Maktoum is the daughter of Sheikh Mohammed bin Rashid al-Maktoum, Dubai’s ruler and the prime minister of the United Arab Emirates. The 32-year-old has not been seen or heard from since she was grabbed by armed men about 30 miles off the coast of India in early March, according to witnesses.

The detailed planning for her doomed escape bid is laid out for the first time in a BBC documentary, Escape From Dubai, through interviews with a French ex-spy and Finnish capoeira teacher who say they helped her plan it, and the Filipino crew that say they tried to sail her to a new life.

Latifa is the second of the Sheikh’s daughters to try to flee a life of a caged luxury and then vanish after reports of recapture. Her older sister, Shamsa, was seized on the streets of Cambridge after fleeing the family’s Surrey estate in 2000, in an apparent abduction never fully investigated by British police.

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Latifa herself said in a video recorded before her escape bid that she had previously tried to leave the UAE aged 16 but was captured at the border, jailed for three years, beaten and tortured. That experience, and that of her sister, meant she was careful in planning a second bid for freedom.

She first reached out to the French businessman and former navy officer Hervé Jaubert in 2011, he claimed, because she read online that years earlier he had escaped from Dubai after running into trouble with the authorities. He scuba-dived out to a boat and sailed to India.

When he got Latifa’s first email, he feared a set-up. “I told her: ‘Look, you are telling me you are the daughter of the ruler of Dubai, maybe it’s a trap and I need to check that you are authentic,’” he told the BBC.

He was eventually persuaded of her identity, and says that for a long time the two wrote to each other every two or three days, even though they would not meet until 2018.

He said that sometimes their correspondence was about logistics, such as when Latifa told him she had saved up $400,000 (£315,000) to pay for the escape bid, but other times it was general commentary on the strange life of a caged royal.

“I’ve been mistreated and oppressed all of my life,” she wrote one day, according to an email shared by Jaubert. “Women are treated like subhumans. My father ... can’t continue to do what he’s been doing to us all.”

In 2014, she met Tiina Jauhiainen, when she came to give lessons in capoeira, a Brazilian martial art, at a royal residence, which she described as a luxurious but oppressive complex. The Finn said she became one of Latifa’s closest friends, a skydiving partner and key to her escape plans, flying out several times to meet Jaubert and pin down details.

The break for freedom began with the two meeting for an early breakfast, which they had done many times before to dull the suspicions of royal bodyguards on the actual day, Jauhiainen told the BBC.

She said Latifa changed her clothes and her sunglasses, and the pair drove across the border to Oman, then set out to sea. They faced a gruelling 26-mile trip by inflatable boat and jet ski, out to international waters, where Jaubert was waiting in a yacht.

He was sailing under a US flag, hoping that would make any attempt to board an international incident, he said, and they planned to head for Goa in India.

“The waves were about a metre and a half and we had the wind pushing towards us so it took many hours before we got to the boat,” said Jauhiainen of the first stage of the journey, out to the yacht.

They were spurred on by fear of what lay behind. In her video statement – meant for release only if the escape bid failed – Latifa said she was braced for severe punishment if captured. “If you are watching this video it’s not such a good thing, either I’m dead or I’m in a very, very, very bad situation.”

Her older sister had escaped for more than a month on a trip to England in 2000. According to a message she sent to a lawyer in the UK, she was smuggled out of the country at her father’s behest after being seized in Cambridge.

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The allegation was passed to David Beck, then a detective chief inspector in charge of Cambridge CID. “Kidnap is a major offence and its not every day that an allegation involving a head of state lands on a police officer’s desk,” he said.

But Beck was not able to take the investigation further. He needed to speak to Shamsa, but when he applied to visit Dubai to do so, the case hit a wall. “A short while later, I was informed that my request had been declined,” he told the BBC. “I was never given a reason why.”

In her video, Latifa said her sister lived in a kind of medical jail, followed and monitored by nurses at all times. She said she saw her sister’s fate as a warning.

From the boat, Jauhiainen said Latifa messaged family, contacted the activist group Detained in Dubai, and reached out to the media, hoping that going public would protect her. But she apparently got little response, perhaps because her story seemed so far-fetched journalists worried it was a scam.

“She was sending emails to reporters and no one replied back to her. Nobody seemed to believe her, so she seemed desperate and sad like you know, who is there to help me now you know they can come after us any day,” Jauhiainen said.

The BBC was told that days later their ship was raided and Latifa was seized. She has not been seen in public since. Her friends say they have not heard from her, and her Instagram account has been closed down.

“She said she preferred to be killed on the boat rather than going back to Dubai,” Hervé said. “I don’t even know where she is. I have the gravest concern.”

Sheikh Mohammed and the government of Dubai did not comment on the allegations made by the BBC in the film or respond to the Guardian’s request for comment. A source close to the Dubai government has been quoted saying she is “with her family” and “doing excellent”.

• Escape from Dubai: The Mystery of the Missing Princess will broadcast on Thursday 6 December at 9pm on BBC2