In the early 1960s, a 17-year-old girl called Helô Pinheiro would walk past the Veloso bar on the beachfront of Ipanema, Rio de Janeiro, every day. She was "tall and tanned and young and lovely" – and she was regaled by the men who drank there.

"When they saw me, they would whistle and shout out, 'Hey beautiful girl! Come over here,'" says Pinheiro, the girl from Ipanema who inspired the song of the same name – which turns 50 today. "I did not know who they were until years later." The barflies she ignored were the composer Tom Jobim and the poet Vinícius de Moraes, who turned desire and frustration into a track that is now second only to the Beatles' Yesterday as the most recorded song in the world, a sultry hymn to unrequited lust that launched the bossa nova rhythm across the world.

Garota de Ipanema – the original Portuguese lyrics are far more poetic than the later English version – was first performed on 2 August 1962, at a small club called Au Bon Gourmet, by Jobim, guitarist João Gilberto and the vocal group Os Cariocas. Three years later, it was an international hit, Gilberto had become a Grammy-winning artist, and lovers across the world were smooching to a whole new rhythm: a mix of jazz, samba and African music known as bossa nova (which translates as "new trend").

And everyone was asking: "Who's that girl?" When the composers revealed their inspiration, Helô, as she is known in Brazil, was astonished. "I told them, 'I don't believe you. You are crazy. There are so many beautiful women here.' But it was me. The song says tall. I am tall. And tanned – I had brown skin from the sun. And young – I was at this time. And I didn't see them. It was true."

Helô became friends with poet De Moraes, who she calls "a dreamer, a charmer who married nine times, who was so clever he became a diplomat". And Jobim? He proposed to her. "Tom was different," she says. "He was shy, he was beautiful, a maestro on the piano. But the two of them drank too much. They were always at the bar drinking whisky, caipirinha, beer." She chose, instead, a steady life with an engineer; they are still married. Jobim, she says, never got over her. "One time, he went to Vinícius's home and told him he only married his wife because she looked like me. He said that in front of her. He was crazy."

Since then, the story of The Girl from Ipanema has morphed into something more akin to a Brazilian soap opera or courtroom drama. In 2001 – years after Jobim and De Moraes had died – their families filed a lawsuit against Helô for using the name Garota de Ipanema for a boutique she opened. "I cried so much, I suffered so much," says Helô, who now lives in São Paulo where she works as a TV presenter, having trained as a lawyer and a journalist. "I tried, but they don't want to speak to me. This situation is so bad." The court ruled in her favour.

Although the song has been covered by everyone from Frank Sinatra (her favourite) to Ella Fitzgerald, from Amy Winehouse to Spike Milligan, Helô has received no direct financial benefit. But it has helped to make her famous. Later this year, she will release a biography and judge a competition in Rio to find a new "girl from Ipanema".

She still loves the song. "It's eternal. Whenever I listen, I remember my past, my younger days. Ipanema in 1962 was a great place. You never saw aggression. Everyone wanted to fall in love. It was the spirit of bossa nova – tranquil and romantic. Today, you don't see composers in the bars and restaurants. There isn't the same inspiration."

The song follows her everywhere, but she does not mind being trailed by the ghost of her past. Two weeks ago, while travelling with her family in Europe, she heard it being played in a London pub where she was having lunch. Did she tell anyone she was the muse? "No," she says. "I stayed quiet, eating my fish and chips."

• Additional reporting by Carolina Massote

• This article was amended on 3 August 2012 because the standfirst in the original said "Jonathan Watts meets Helô Pinheiro"; the interview was conducted by telephone.