The film, called “Someday Melissa” and now in the editing stages, has become for Ms. Avrin salve, distraction and cause — a way to get the word out to other families grappling with eating disorders that they are not alone; to sound the alarm that eating disorders have the highest mortality rate of any mental illness; to help make sense of the senseless event that was losing her teenage daughter.

Image FAMILY Above, Melissa Avrin with her brother, Andrew, at Thanksgiving time in Utah in 2007.

“I kept saying, ‘This is an amazing way for me to channel my grief,’ ” Ms. Avrin said. “But it also allowed me to put off grieving.”

Ms. Avrin, 56, got the idea for the film from one of Melissa’s therapists, Danna Markson, who introduced her to Jeffrey Cobelli, 27, a filmmaker. Over the last several months of working on the project, Ms. Avrin has come to know more than she ever intended to about eating disorders — how their seriousness has been underestimated, their treatment underinsured, their deaths underreported.

The process hasn’t been easy, and some, like her ex-husband, initially questioned the impulse to do it at all. Melissa’s best friend since first grade, Nicole Kendrick, who also suffers from an eating disorder, said she was incredulous when she first learned that Ms. Avrin was making the film. “I thought she was crazy,” Ms. Kendrick said. “I guess I didn’t realize how deep a mother’s love can run.”

But Ms. Avrin said that making the film has been easier than doing nothing at all. “I’ve never once thought this was more than I could bear,” she said, in an interview at her home in Totowa, N.J. “If anything, the more I continue, the more I know it’s the right thing to do.”

The difficulty of reliving her daughter’s decline has been mitigated by the public response. “Sometimes I think: ‘I’m a suburban mom. Who am I to think I could make a difference in the world?’ ” Ms. Avrin said. “But then I read the messages that keep coming in from people I know and people I don’t know who say Melissa’s story has motivated them to fight one more day.”