Before she died, teen worked hard on film about her horrible illness

If you should someday see a movie called The Magic Bracelet at a local screening, it will be because of two things:

A child's dying wish. A parent's final promise.

And also, perhaps, some real Hollywood magic.

Cheltenham teenager Rina Goldberg wrote the story of sisterhood and friendship, developing the plot and characters even as mitochondrial disease stalked her body organ by organ.

She was 15 when she died in December.

Strong? Sure. Smart? Definitely. But mostly insistent. Determined that what began as a distraction from catastrophic illness should appear on the movie screen and spread her life lesson:

Love one another. Make each day count. Dream big.

"It's not a memorial to her," said Rina's mother, Stacy, a speech therapist at United Cerebral Palsy. "She wouldn't want it for the sake of herself."

She wanted it for others, crafting a tale of a mystical bracelet that links two girls - a metaphor for her relationship with her friends. One character has "mito," where cells generate less and less energy, eventually causing whole systems to fail. There's no cure.

Rina was frustrated that the disease got little attention although it affects one in 4,000 children. At the same time, she didn't want her movie to be a public-service announcement. It had to be a solid, entertaining film.

"She took her creativity, and her imagination, and let it go free," said her father, Ari, director of the Jewish Community High School at Gratz College.

Mitochondrial disease causes overwhelming fatigue, and from the time Rina was young, exhaustion was her companion. By 11, her heart struggled to stay in rhythm. A stroll through the mall became a marathon, and a cold could land her in the hospital.

Three years later, at a particularly difficult time, family friend Mitch Eiven, who runs a movie-production company near Princeton, asked Rina if she wanted to make a film.

She did. In fact, she seized on it. Rina would write out her concepts and e-mail them to Eiven, who turned her thoughts and direction into dialogue and narration, then returned the pages for revision.

"She became a filmmaker," said Eiven, head of the Movie and Theater Corp.

She was always more than her illness. Rina's stomach may have been connected to a feeding tube, but her ears were plugged into an iPod, and her mind roamed the landscape of pop culture. The canons of Twilight and Harry Potter were her specialty, the music of Taylor Swift her soundtrack, and if people needed details on American Idol, they knew who to ask.

Rina led weekly movie-production meetings, where friends younger and older helped tweak the script even as its author grew weaker. Over time, she lost the ability to drink. And then to read. And then to walk. She also lost two close friends, to cancer and mitochondrial disease.

In June 2010, though homebound, Rina took a seat in the producer's chair and led a formal, live read-through of The Magic Bracelet. And yes, she actually said, "Quiet on the set!"

"In 16 years of being a nurse, I've never seen a child with such determination," said Shannon Buffler of Keystone Hospice.

One morning in September, Rina woke up sobbing. She'd dreamed that her lost friends, Amanda and Kevin, had come down from heaven to fetch her.

"Maybe you're missing them," her mother said, trying to soothe.

"No," Rina insisted. "I saw it."

And in fact she was failing, racked by body pain and headaches. Rina knew she was leaving. And she needed to be sure her movie would get made. That people might learn of the suffering of children, that they could be moved to help.

In early December, she barely had strength to speak. She looked at her mother.

"You promised, right?"

"I promised," she answered.

Rina turned 15 on Dec. 16. She died 13 days later.

Last week, her parents got word that the Los Angeles-based Make a Film Foundation (MAFF), similar to the Make-a-Wish Foundation, would enlist professional actors and directors to develop Rina's movie. Foundation mentors include the actress Laura Innes, known from the TV drama E.R., and the actor Elijah Wood, who played Frodo in the Lord of the Rings trilogy.

Like other foundation films, The Magic Bracelet will open with a red-carpet Hollywood premiere, followed by various screenings around the United States.

"We're creating it with Rina's spirit," said Tamika Lamison, executive director of MAFF. "She may not physically be here, but she's already done all of the work."