The old stone bridge runs below a modern, metallic crossing that she leapt from.
Miss De Abreu was left dangling lifeless from the rope as her aunt watched on in horror.
Specialist rescuers took 25 minutes to reach her and pronounced her dead after freeing her from the bungee cords, laying her body on the tarmac under a blanket.
The spot, around 260 feet above sea level, is used by several adventure sports firms.
Thrill-seekers usually fall for about 20 metres and swing underneath the stone bridge, with a first jump offered for around £24.50.
A spokesman for the Guardia Civil in Granada said: "(Miss De Abreu) was staying with her aunt for a few days and that relative was present when the tragedy occurred at the Tablate Bridge in the Alpujarras area.
"When emergency services arrived the deceased was still hanging from the rope.
"Although it is too early to draw any conclusions about the circumstances of the death, one of the lines of inquiry is that there was a miscalculation with the rope."
Miss De Abreu was born in London but her parents separated when she was very young and her mother took her to her native South Africa.
She was raised in Cape Town but after graduating from the Cape Peninsula University of Technology she decided to return to the UK in order to learn more about her British heritage and settled in Brixton, south London, in March.
She had only recently been reunited with her British father, whom she had not seen for 23 years.
A relative told the Daily Telegraph that she had gone travelling around Europe with her boyfriend and was staying with an aunt and cousins in Spain when the tragedy occurred.
A Foreign Office spokesman said: "We are urgently looking into reports of the death of a British national in Spain and stand ready to provide consular assistance."
An investigating judge has launched a probe into the tragedy.
He is expected to call a series of witnesses in for questioning after analysing police reports and ordering specialist assessments of what went wrong.
One theory is that there was a miscalculation relating to the length of the rope.
A local website describes bungee jumping from the bridge was a "hair-raising" experience due to the closeness of the ravine walls during the fall.
Another boasts: "If you want a huge dose of adrenaline this is your bridge."
Lanjaron is about 35 miles from Granada on the southern flanks of the Sierra Nevada mountain range and is famous in Spain for its mineral water.
The region is popular with expats and near to the hippy village of Orgiva, which attracts people living alternative lifestyles from all over the world.
