The product of a strict Catholic upbringing, she started helping out with the company at age 15, sticking labels on bottles of shampoo and mixing cosmetics.
In October 2011, a court ruled Ms Bettencourt was suffering from a form of dementia, and awarded the daughter control over her mother's wealth and income - then estimated at $26 billion and including about 33 per cent of L'Oreal.
Bettencourt is survived by her daughter, Francoise, who was born in 1953.
Schueller, the son of bakers from the eastern Alsace region, initially named his company Aureale, but changed it to L'Oreal in 1939.
Bettencourt was the only child of L'Oreal founder Eugene Schueller, she inherited his fortune following his death in 1957.
She only had one child, daughter Françoise Bettencourt-Meyers, who has two children. "Who always looked after L'Oreal, the company and its employees and was very attached to its success and development".More news: S&P downgrades Pennsylvania credit to A-plus, cites budget problems
Sarkozy's former campaign treasurer, Eric Woerth, was acquitted on charges of "abuse of weakness" and taking donations from Bettencourt during the 2007 presidential election campaign.
Both her father and her husband Andre Bettencourt were accused of being ardent Nazi collaborators during World War II.
Bettencourt's name has been involved in a politico-financial scandal known in France as the "Bettencourt Affair", which has wound its way through French courts and newspapers for years.
Bettencourt had served as the chief executive officer of L'Oreal till 2012, after which she took a retirement from her professional life.
As the world's leading beauty company, L'Oreal generated sales amounting to 25.8 billion euros in 2016 and employs 89,300 people worldwide, according to the company. The company owns brands like Lancome, Garnier and La Roche-Posay.
L'Oreal also owns The Body Shop.