“She has this grand vision; she wants to be the one-stop shop for filmmakers,” said Michael Benaroya, 30, a member of a Seattle real estate family who has joined Ms. Ellison in financing a thriller called “Catch .44” and “The Wettest County in the World,” a Prohibition-era crime drama, both of which still await release.

Ms. Ellison declined interview requests.

Friends and business associates describe her as shy, though not too shy to have reportedly posted on MySpace a photo of herself with the caption: “Drunk dialing Dad in Paris after 3 bottles of Dom.” Like her father and brother, Ms. Ellison is not a college graduate, though both she and David attended the University of Southern California’s School of Cinematic Arts (David is enrolled there, and planning to graduate, according to the school.)

But she is not without focus. A competitive equestrian, she trained on jumpers at the Wild Turkey Farm in Woodside, Calif. Seven years ago, Ms. Ellison rode in the North American Young Rider Championships.

According to an associate who spoke on the condition of anonymity to avoid conflict, Ms. Ellison has had unusually broad life experiences because of her father’s wealth. David Geffen, the DreamWorks co-founder and for a time the co-owner of a yacht with Mr. Ellison, is said to have been a longtime mentor. (Mr. Geffen did not respond to an e-mail query.) Ms. Ellison works with the Ziffren Brittenham law firm, an entertainment powerhouse that has represented both DreamWorks and her brother.

Her introduction to the film business began in 2006. Katherine Brooks, a writer and director of television programs and indie films, recalls Ms. Ellison contacting her via MySpace after the first showings of Ms. Brooks’s movie “Loving Annabelle,” about forbidden love between a teacher at a Catholic school for girls and her student. Out of the blue, Ms. Ellison, said she wanted to invest in Ms. Brooks’s next picture.

At a first meeting, Ms. Ellison “drove up on a Harley-Davidson, black-painted nails, this Pink Floyd shirt and jeans,” said Ms. Brooks, who spoke by telephone from New Orleans, where she now works. For a year, the two made plans for “Waking Madison,” about a woman who tries to cure her multiple personality disorder by locking herself in a room without food for 30 days.

Ms. Ellison wrote checks for a budget that was reported to be $2 million, though Ms. Brooks said she “didn’t want to know” what the film actually cost. Shot in 2007, it was shown at the Newport Beach Film Festival in May of this year, and was finally released on video in July.