EXCLUSIVE: 'Before I Fall' Director Ry Russo-Young on Mean Girls and Alternate Endings

Director Ry Russo-Young forgot to feel the pressure. The Sundance ingénue's latest feature, Before I Fall, is an adaptation of the best-selling Y.A. novel about a somewhat reluctant high school mean girl, Samantha (Zoey Deutch), who meets her early demise in a car wreck, only to wake up the next day...and the next day and the next day on a seemingly endless loop.

Despite tween fans' rabid protection of their most beloved books and the fact that they can live in her Twitter mentions for the rest of time, Russo-Young isn't fazed -- or wasn't. "Uhh, you're freaking me out!" she joked during a recent call with ET, before explaining, "I actually took great comfort in the fact that I could look online and see what fans connected to about the book, what lines they were holding dear to their hearts, what moved them. Then those things, to me, were like, 'I have my marching orders.'"

WATCH: ET's 'Speed Date' With Zoey Deutch! Get to Know the 'Before I Fall' Breakout Star

ET: Were you able to collaborate with [Before I Fall's author] Lauren Oliver? Or have her involved in the movie-making process?

Ry Russo-Young: Yes, absolutely. We had conversations when the movie got greenlit. Or at some point even before that, she and I got on the phone and talked about, like, "What is this book really about to you? What is important to make sure it makes it to the screen? How attached are you to X, Y, Z?" And that was really helpful.

Have you gotten her review of your final film?

Oh, yeah. She loves the film. Absolutely.

That must be such a big relief for you.

I will say that she came to set -- and she only came to set one day -- and she did kind of freak out when that happened. I think it was just because the book is so personal to her, that she was like, "I can't handle this. This is, like, so real. This is really happening." It kind of gelled for her. And I was like, "Oh no! The author is hiding in a closet! Uh oh!" [Laughs] "Did I do something wrong?!" A real moment of self-doubt, then and there.

I've heard that this wasn't the easiest shoot, especially for Zoey, because she had to film multiple "days" of the movie during one day of shooting. How was that for you?

It was also very complex. Because the movie is like a math problem. Any movie, when you shoot it, is very complicated because you're shooting out of order. So, on this movie it was almost doubly complicated, because you're shooting out of order, but you are shooting the same day over and over again. So, you're shooting the same scene but different things are different in each scene, but you want to shoot it from the same angle. It's very hard on the actor, but it's also hard on the director to organize. What's the best way to shoot this? How am I going to give the actor the clarity they need for each day? How's each day going to look and feel different, in light of the fact that we're block shooting and don't really have enough time to do it? It was just a big, challenging math problem, which I really enjoyed cracking. The first thing I did was put it up on my wall in terms of each day and color code each scene, so all the school scenes were blue and all the home scenes were red and stuff like that. I could really look at it big picture.

How do you make a teen movie like this feel modern and timely, but also not immediately dated when the next new technology or app or slang comes out?

I think ultimately what I looked at is, what are the teen films for me that are evergreen, that stayed with me? Even if a film like The Breakfast Club, for example, it might look dated to us now, but those ideas of what that film is -- that you're going to be your own person and not be what your parents want you to be -- that never gets old. That's never dated. This movie will inherently date, of course. Every film does. Like, It's a Wonderful Life looks dated, but the themes are eternal and the ideas behind it and the emotions will last forever and still resonate with us and still make audiences feel and cry. So, I try not to sweat the contemporary technology or ideas and focus on what will last forever.

Did you have conversations about how mean to make the girls (Deutch's onscreen squad of Halston Sage, Cynthy Wu and Medalion Rahimi)?

Certainly. We definitely did some range in there in terms of, like, Let's try a take where you guys are meaner. Let's try a take that's, for lack of a better word, kinder! That was a moving scale that we certainly played with. We needed to have them be quote unquote mean, and even mean within their crew to each other. That was a big piece of it -- the internal put-downs within the group. There's always this power struggle within the girls, but then also [there is] a lot of love there. It was a fine line of creating those relationships and [finding] the line between affection and cruelty, which is sometimes very, very thin when it comes to teenage girls.

Zoey is so, so good, and I think this is really going to be a big breakout for her--

I hope so. I think she deserves it.

What made her right for the role, for you?

A big part of what made Zoey so incredibly perfect for this part was range. She's really playing six different roles. You need an actress that's going to be able to be the follower mean girl -- the popular, fun, I'm-losing-my-virginity kind of movie teen girl on day one. And then you need the confusion of day two and the moral awakening on day three and then the f**k-it-all, angry-girlnihilist on day four, the kind of good girl on day five, and the, like, hero -- the ultimate I'm-going-to-fix-this-and-run-through-the-woods-and-make-it-right hero -- on day six. Range was really critical and that's what I was so impressed with in terms of Zoey. This is a drama, and she's also a comedic actress as well. Zoey Deutch can do anything, in my book.

People who haven't read the book may be surprised by the ending -- I certainly was. Was there ever any point in the process where you consider making any big changes to that ending?

Not really. It was kind of like a joke, almost. Because the book is so clear from the very beginning that she's dead, and the movie actually is pretty clear from the get-go that she's dead, too. Lauren's thing from the very beginning was, "The way to f**k up this movie is to make her live." That was so clear, and that was something that producer Jon Shestack and I talked about a lot. Like, the Hollywood ending of this movie, in the most clichéd sense, is like, And she opens her eyes at the end. And did we shoot that? Ab-so-lutely! With the intention of using it? Not at all. We were like, "Let's shoot it to have it and then try to not use it." Because that's not what the DNA of this project wants to be [or] what this movie is.

The movie screened at Sundance earlier this year, which was your third time there (after You Won't Miss Me in 2009 and Nobody Walks in 2012). Was there anything that made this time feel different?

Yes. Well, first of all, we already had distribution, and for a director, that is a huge deal and made the entire process a lot less nerve-wracking. I wasn't super worried about, Oh my god, are we going to sell the movie?! It's really hard to separate yourself of like, "Does the movie quote unquote win or fail based on those metrics?" It was a relief in that sense and it freed me up to be able to enjoy the cast and the fact that a lot of the crew was there and enjoy the audience's reaction to the movie. A lot of people came up to us, like, crying after the screening and saying, "Oh my god, you've made our relationship better." And then I start crying and then Lauren starts crying.

It was a really fun experience, in that way, and we also premiered the movie on the day of the Women's March. And we marched in the morning before our screening. Literally right before our screening I went to the march. So, it was incredibly meaningful in a lot of ways, to make a movie that is talking about how you treat other people on a day where women are uniting all over the world for equality.

This movie is also directed by a woman and stars women and was produced and written by women. Was that something that was important to you?

It wasn't planned. It was kind of a happy accident and I think it's a wonderful thing that it happened. But it wasn't like, Well, I won't do this movie unless it's written by a woman! You know? I think the movie has a real sense of female authenticity and an underlying hero's journey, and seeing the classic hero's journey from a female perspective is actually quite feminist.