Lily Collins says her struggle with an eating disorder was an "entire physical experience"

She said: "It was an entire physical experience, emotional experience. But I was supported, and it's a really important story to tell."

And Lily says the movie - which premiered at the Sundance Film Festival over the weekend - tackles the "taboo" subject in a way that makes her "proud" and "excited".

She added to 'Entertainment Tonight': "It's a topic that is taboo, I think, with young girls, and it's really important to tell a story with this subject matter in the way that we tell it.

"And, I'm so proud of it, and I'm excited that we're going to Sundance."

Meanwhile, 'The Mortal Instruments' actress - who is the daughter of music legend Phil Collins - recently said the role helped her face her "fear" of eating disorders "dead on".

She said: "This was definitely a more dramatic role for me. I suffered with eating disorders when I was a teenager as well.

"I wrote a book last year, and I wrote my chapter on my experiences a week before I got [writer-director Marti Noxon's] script. It was like the universe putting these things in my sphere to help me face, kind of dead on, a fear that I used to have.

"It did require a different set of emotional skills, to go back in time for me, with my experiences. So definitely a different type of film for me to do, very, very personal."