NEW YORK — Actress Mary Elizabeth Winstead has been developing quite the career for herself in the commercial sector. Parts in “Final Destination 3,” “Black Christmas,” “Grindhouse,” “Live Free or Die Hard,” “Scott Pilgrim vs. the World” and “The Thing” have been a slow build for the actress, right up to this summer’s “Abraham Lincoln: Vampire Hunter.” But while she’s always showed a spark that promised more, it didn’t really hit full bloom until James Ponsoldt’s “Smashed” premiered at Sundance back in January.

And indeed, the Sundance experience meant a great deal to Winstead, who grew up in Salt Lake City and always saw the fest as something of an El Dorado. “Sundance was always a big goal of mine, since I was a kid,” she says. “It was always like this thing that was so close but I could never find my way into actually being a part of it. It was pretty emotional. Yeah, I think I broke down several times when I was there so it meant a lot.”

In the film, Winstead stars opposite Aaron Paul (TV’s “Breaking Bad”) as an alcoholic caught up in a co-dependent relationship, hiding all the embarrassment and lies that come with addiction. It’s similar in that vein to Robert Zemeckis’s “Flight,” which closes out the New York Film Festival this weekend. Unlike “Flight,” though, “Smashed” is a bit of a dark comedy, with plenty of emphasis placed on the “dark.” But Winstead says when she first read the script, she knew one thing: she had no idea how to play the part.

That was kind of the first step toward understanding what she might have to tap within herself to carry across a certain authenticity. After that, she says, it became all about looking at herself and her own own life, her own issues, and digging deep to figure out what those were.

“I drew from my own personal life, but it was very non-literal,” she says. “It doesn’t have to be anything like alcohol. It doesn’t have to be a substance at all. For me it was more about relationships in my life that were maybe toxic or co-dependent that I was keeping myself in because they sort of validated my pain in some way, and I kept sort of going through the cycle, even though it wasn’t really doing anything positive for my life and they weren’t making me happy at the end of the day.”

Which is a nice segue into her work with Paul, who hasn’t broken out on the big screen just yet because he’s been a little busy winning Emmys for his work in AMC’s “Breaking Bad.” The two actors carve out a wholly believable “toxic” relationship, as Winstead says. Anyone who has been in a situation of co-dependency will instantly relate. And Winstead has nothing but love for her co-star.

“He’s so great,” she says, smiling big. “He’s so talented and just the sweetest person you could ever meet, just open and warm and generous as an actor. He really just wants to give you whatever you need in order to go to the place you need to go to. But even when he wasn’t on camera he was giving me so much. He was just lovely.”

As Winstead’s character goes on her journey throughout the film, however, it becomes an issue of leaving that toxicity behind, and all the pain and heartbreak that comes with that. This is a SPOILER, so skip this and the next paragraph if you don’t want to know where the film goes, but the ending is interesting. Following a full year of sobriety, Winstead’s Kate visits Paul’s Charlie one more time as he’s trying to get his own life together. They play a game of croquet, as they used to do wasted in their back yard together, and before the film fades out, Charlie asks if they can play one more game. In some ways it could seem like the same unfortunate cycle is creeping back in, but in others, it could be seen as hope for the future. Personally, I like to see it as the latter.

“For me, when I first read it, I think I had that same response,” Winstead says. “It’s such a great love story of these two human beings who have problems and make mistakes but they’re trying to be better. After researching the role, my take is kind of different on it now. But I don’t think any take is wrong, it’s just how you look at it.

“For me, having gone to AA meetings and talked to a lot of people, it just seems like the wrong thing for her to do, to put herself back in that situation, even if he does get sober, even if he does really get his life together, they just have such a history of toxicity, those memories being constantly put back in their lives would be a constant temptation for them to go back to drinking. So it’s just not a healthy thing to do. But what I love about the ending is that it feels like the beginning of his story. It feels like the beginning of his journey to becoming an adult and becoming a better person, so I like that it’s really hopeful in that sense, that you feel like down the line they’re gonna be at least friends. They’re gonna be okay. Which is great.”

You can come back from spoiler-land now.

Finally, Ponsoldt was “incredible” to work with, Winstead says. Calling him “the epitome of an actors’ director,” she praises his effortless communication and really digs in to pin-point what it is about his handling of the material that worked for her.

“He already understands where you’re coming from as an actor,” she says, “so that’s the language he speaks. He speaks in emotions. He doesn’t speak in results. He tells you what you should be feeling as opposed to what you should be doing. So those things make it so much easier as an actor because you don’t have to translate in your head that, ‘Okay, the director tells me I have to do this but I have to look at it from a different perspective.’ You can just listen to him and go straight into doing it without having to sort of rethink it in your mind.”

The Best Actress race finally started filling up this season with the rise of players like Jennifer Lawrence and the addition of others like Helen Mirren. So calling it a thin race ripe for the picking is no longer all that accurate, but nevertheless, a performance like Winstead’s deserves a hard look amid the fray of typical contenders. She gives everything to the role and her character takes a significant journey. She’ll get support from Sony Pictures Classics, which has a few other contenders in the race as it is, but whatever happens, it will be easy enough to point to this moment as the one in which the actress started to break out and deepen her craft, a beginning of sorts.

“Smashed” opens in limited release on Friday.