MArie Callas (1923-1977) is often celebrated as one of the greatest sopranos of the 20th century. She is best known for her performances in operas Medea, Tosca And La Traviataand when TIME put her on the cover of the October 29, 1956 issue, the magazine called her “the undisputed queen of world opera.”

But Maria, The Netflix biopic starring Angelina Jolie as Callas, which is released today (December 11th), is not set at the height of her career. Rather, it takes place at the lowest point. Set in the last week of her life, Callas is living in Paris and looking back a lot because she feels like there is nothing to look forward to.

A biopic about her life might have been a dream come true for the New York-born singer, as she loved being the center of attention, according to Callas’ biographers. But the film doesn’t glorify Callas, instead portraying her as sad and withdrawn. TIME examined why she found herself in a very dark place at the end of her life.

Callas’ mental health

Callas was known for his big ego. In one scene she announces, “I come to restaurants to be worshiped.” She tells everyone that she is writing an autobiography and an aria – neither of which she has done in real life.

When she performed, she tended to create a scene. “She was known for leaning in and shaking her fist when people hissed or booed,” says Lyndsy Spence, author of Casting a Diva: The Hidden Life of Maria Callas. She had a terrible temper and there are many scenes in it Mary where her character has little patience for people.

Throughout the film, Callas hallucinates that television cameras are following her and acts as if she is being interviewed even though no one is there. In the film, she regularly takes Mandrax, a highly addictive sedative that can cause hallucinations, and in real life she was actually addicted to the drug.

After speaking with the daughter of Callas’ neurologist, Spence believes the singer may have suffered from a neurological disorder on the multiple sclerosis spectrum. Toward the end of her life, Callas “physically can’t control her voice or muster the strength to sing, and that obviously escalates to the point where she can’t live with it anymore,” says Spence. “In the late 1970s, she began self-medicating to manage symptoms and unfortunately became dependent on prescription medications, including Mandrax.”

Paul Wink, professor of psychology at Wellesley College and author of Prima Donna: The Psychology of Maria Callas, argues that she would likely be diagnosed with depression and drug addiction today. “She died addicted and desperate” he says.

Callas and Aristotle Onassis

Callas’ relationship with Aristotle Onassis, the Greek shipping mogul, could be the plot of an opera. He actually hated the opera, but he loved the scene and the glamor of it all.

“What he liked was the party afterward, where he and she were the center of attention backstage,” says John Louis DiGaetani, author of The Ultimate Diva: The Life and Career of Maria Callas.

Callas wanted him to marry her, but he left her for Jacquline Kennedy, the widow of assassinated President John F. Kennedy. As the film shows, Callas really figured it out while watching the TV news in Paris.

“He collects rich and famous women,” says Spence.

There were rumors that Callas was once pregnant with Onassis’ child. The biographers TIME spoke to say there is no evidence that this is the case, but if she were to give birth to anyone’s child, it would be Onassis’s.

In the film, Callas is told, “Jackie was his wife, but you were his life.” The marriage between Onassis and Kennedy was not a happy one. By the time Onassis realized that Callas was the love of his life, it was too late to rekindle their relationship. He died in 1975. Callas never recovered from this loss.

Callas at the end of their lives

Callas was “lonely, disillusioned, basically fed up,” as Spence describes the singer in her final days.

In the film, as in real life, she spent most of her time playing cards with her butler and maid and looking after her dogs.

She was estranged from her family. Her mother was a stage mother who pushed her into the opera because she desperately wanted to make money with her daughter’s voice. In one scene in the film, her mother asks her for money, and there is some truth to that. According to Spence, her father once acted as if he was dying of cancer and needed her help to pay his medical bills.

She found it difficult to find meaning in her life beyond opera. “When she developed a relationship with Onassis, opera was no longer her life – Onassis was her life,” says Wink. “It would have been nice for her to find her own identity, but she couldn’t. That’s why she lived in despair. So she took Mandrax and became a hermit.”

Callas was found dead in her Paris apartment at the age of 53. The cause of death was a heart attack.