As she arrives for the Oscars, the producer of The Master and Zero Dark Thirty is no longer the mystery she was

Photographers should be able to recognise Megan Ellison as she arrives at the Oscars this Sunday. Dark-haired and a young-looking 27, the producer of two of the year's most contentious films – The Master and Zero Dark Thirty – is no longer the mystery she was a couple of years ago. Yet the most powerful new force in Hollywood may still go unnoticed.

"She's incredibly self-effacing," says JoAnne Sellar, another of The Master's producers, who has worked with that film's director, Paul Thomas Anderson, throughout his career. "If you ran into her on set, you'd assume she was someone's PA."

For an industry fond of tales of secretive billionaires with extravagant superpowers, there is something strangely fitting about the rise of Ellison, the daughter of software tycoon Larry Ellison, third wealthiest man in America. She herself has yet to give the media a formal interview – but her importance to the film business is seismic.

In the last two years Ellison's Annapurna Pictures has backed not just its pair of Oscar contenders, but a raft of films involving actors Brad Pitt and Gary Oldman, plus directors including Hong Kong auteur Wong Kar-Wai.

The money involved is dizzying – The Master and Zero Dark Thirty reportedly cost $80m (£52m) combined, all of it paid by Ellison.

Of course, Hollywood has always found room for rich outsiders – as far back as 1932, scriptwriter Ben Hecht was calling independent producer Howard Hughes "the sucker with the money". Even so, Ellison cuts a striking figure, not just as a woman and one so young and lavish, but because of her role as patron saint of the kind of smart, economically risky movies which in 2013 would struggle to exist without her.

"As a film lover, I think she's a godsend," says Ted Hope, the veteran indie producer whose CV includes a long relationship with director Ang Lee.

"She's the only one out there putting reasonable budgets behind adventurous movies for adults that are 100% their directors' visions."

At the high end of the film industry, the relief she inspires is palpable – so much so it has taken until now for scepticism to surface. But before either the gratitude or the barbs, there was simply puzzlement over the identity of a woman who had essentially walked in off the street with a sackful of cash.

The source of that wealth was the easy part. In America, Larry Ellison is a financial celebrity – a flamboyant Silicon Valley mogul whose late friend Steve Jobs was official photographer at his fourth wedding in 2003. But little was known of his daughter. In her teens, she rode horses competitively. Later, she attended but did not graduate from the University of Southern California's school of cinematic arts.

Now, the picture that emerges is a focused young woman who long ago swapped the horses for a Harley-Davidson motorcycle, dresses pointedly down in jeans and Led Zeppelin T-shirt, and is, according to Sellar, "a real movie lover – she's great just to hang out with and talk film".

While Sellar speaks of her quietness, Hollywood journalist Sharon Waxman carefully details other qualities: "She's smart, hot and she's confident." Meeting at a party at the Cannes film festival, Ellison affably told Waxman she felt the press mistreated her father, and "just didn't want to go there" when it came to interviews. Now, Waxman says, "she pays her PR to keep the press away".

Ellison's only nod to public life comes via Twitter, where updates about her films accompany personal titbits and quotes from Oscar Wilde and Yoda. Her movie career began, however, in the distant age of Myspace – which she used in 2006 to contact director Katherine Brooks, whose film Loving Annabelle she admired enough to offer $2m for a little-seen follow-up, Waking Madison. A higher profile credit came in 2010 when she and older brother David invested in the Coen brothers' True Grit.

But in Hollywood, her name abruptly became big news in January 2011 when, on turning 25, she received a lump sum from her father. The figure, never confirmed, is often reported as $2bn.

For one of her film-making heroes, the timing was faultless. At this point, despite the acclaim Paul Thomas Anderson received for his previous film, There Will Be Blood, The Master looked like a movie that would never be. The year before, original backers Universal had withdrawn its funding – Sellar says rumours the film was an attack on Scientology did not help attract investors.

Then came an unexpected call from Anderson's agents, the omnipotent CAA, who had begun finding Ellison movies to fund. She was, they explained, "a big Paul fan". With a figurative click of her fingers, the film was saved.

"She was this angel sent from heaven," Sellar says. A budget was swiftly agreed, before Ellison "left us to it" to make the story of a troubled second world war veteran. Could the film have even been made without her? "Not the film you saw."

But Anderson was far from the only director in limbo when Ellison appeared. Since the economic infernos of 2008, corporate Hollywood has been unprecedentedly risk-averse. With the money lake dried up, countless big-name film-makers have been stuck piecing together movies with precarious jumbles of private equity.

A deal with Ellison is different. The Master was financed down to the last cent, that support secured in a single meeting. In return, her most immediate reward seemed the warm glow of Medici-like patronage, becoming a regular visitor to Anderson's set. (Though Waxman suggests she also enjoys mixing with the industry's upper orders at awards ceremonies.)

Her approach was similar with Zero Dark Thirty – director Kathryn Bigelow's account of the CIA's hunt for Osama bin Laden. Again, Ellison funded the entire film alone. This time, however – according to a recent Vanity Fair profile – she also helped recruit its star, Jessica Chastain, with whom she became close friends, travelling to the Middle East for a shoot which found Ellison, Chastain and Bigelow wearing burqas to film in a Jordanian mosque.

Yet while the result is up for best picture at the Oscars – with five nominations in total to The Master's three – Bigelow's film provoked controversy over its view of the use of torture. While Sellar doubts that unnerved "the only person with the balls" to back her own hot potato movie, the rancour was fierce, and is thought to have cost Bigelow a best director nomination ("So fucked up #recount," Ellison tweeted.)

Meanwhile The Master, although lauded critically, disappointed at the box office – and the money it lost triggered a backlash. The same unqualified support of talent that earned Ellison thanks from Anderson's fans is, to others, a dangerous indulgence.

"I don't think she's spending money wisely," Waxman says, claiming the film's budget was excessive. "I don't think it's healthy for the quality movie business to make movies that won't make their money back."

In this version of events, Ellison risks doing to the film industry what super-rich club owners have done to British football – inflating its economy and threatening disaster if they walk away. On that point, Waxman is pessimistic: "However rich you are, the excitement of sinking your money into movies will end if you keep losing it."

Elsewhere, things have got personal. Vanity Fair's portrait was flecked with unattributed complaints about the subject's "rich-itis", including a neglect of Hollywood protocol in which, at the highest levels of power, emails and phone calls are returned quickly and personally.

Yet her business affairs may not be naive. Despite or because of the controversy, Zero Dark Thirty has become a box office hit, soaking up losses made on other films. Tellingly, she also has a financial stake in reviving the potentially lucrative Terminator action series. And while some aspects of her personality may recall F Scott Fitzgerald's maxim that the very rich are "different from you and me", Ellison's embrace of the lucky few guarantees potshots from the unlucky many.

Her skin may be thickening anyway. One Vanity Fair source described her being so traumatised by the famously volcanic Harvey Weinstein (who distributed The Master in the US) she would probably never work with him again. A week later, the two struck a deal for Weinstein to distribute Wong Kar-Wai's martial arts epic The Grandmaster.

While Waxman may yet prove prophetic, the short-term future is all about expansion. Among the myriad films Ellison has pending are work from director David O Russell, a study of Julian Assange scripted by Zero Dark Thirty writer Mark Boal and another Anderson movie – this time an adaptation of Thomas Pynchon's novel Inherent Vice.

By the end of which we will probably know no more about her. Where Weinstein courted the press, the sheer scale of Ellison's wealth means she simply does not need to.

But perhaps what we have should be enough: "I'm happy just to have this person here," producer Ted Hope says, "pushing culture forward." In other words, if it's Megan Ellison's world and the rest of us just live in it, at least there's something good on at the movies.

Curriculum vitae

Born 31 January 1986

Career The daughter of billionaire Oracle CEO Larry Ellison, she took up independent film producing in 2006 and subsequently founded Annapurna Pictures.

High point Winning the American Film Institute award for best film for Zero Dark Thirty: the citation called it "a definitive tale of our times, where the battle waged is one of intellect over arms".

Low point The political controversy that overtook hit the film over how it depicts torture.

What she says She does not do interviews. She expressed her displeasure at Kathryn Bigelow's lack of an Oscar nomination for Zero Dark Thirty on Twitter.

What they say "Sometimes when you're a woman, people judge you a little more harshly. I think that if Megan was a guy people wouldn't be jumping on her as much" Amy Pascal, co-chair of Sony Pictures Entertainment, 2013