In Pines, directed by Derek Gianfrance, Mendes looks haggard, hardly the hottie we have come to know or the hilarious comedienne who had us in stitches in the Farrelly Brothers' Stuck on You. In a story that spans 17 years, Mendes lost 6.8kg for the early scenes.
"That's a lot because I'm a little girl," she says. "I wanted it to feel like my baby had sucked the life out of me, literally and figuratively. Of course, I loved my child but the stress of the predicament I was in depleted me so I saw her as unsexy and unflattering in that outfit."
"Oh that's Derek," she says in explanation of the old shorts she wears. "He encourages you to bring your own wardrobe and since the movie took place in the early 90s, I still had some stuff from then."
Born in Miami, Florida, to Cuban parents, the youngest of four children, Mendes was raised by her mother following her parents' divorce. They maintain a close bond, so her mother became a huge influence on this movie.
"When it came time to cast [the mother role] Derek said, 'Okay, so you are going to go pick your Mum. Find the woman you have the right connection with.'
"I auditioned 20 women and Olga Merediz was the one who reminded me of my mother . Something about her was so maternal and beautiful. Ironically, she doesn't have children but she is Cuban and I felt an immediate connection."
Gianfrance encouraged Mendes to draw on her personal experiences and wanted to know all about her.
"I took him for a drive to the Silver Lake Echo Park area and I showed him the first place where I lived when I came to Los Angeles. I showed him what school I went to, our first little house."
Mendes admits to making an extra effort to be cast in the role. "It was so special.
I love that the film is so thought-provoking. I think there is no answer - there are many answers."
Mendes likes to chase directors she wants to work with, as she did with Gianfrance after she saw Blue Valentine.
"I go for it. Absolutely. I've written Mike Leigh three notes at this point and the message is not getting through. So, if you can help me out, say, 'Mendes really wants you!' I do a great Cockney accent, by the way."
She has worked with Hollywood's top stars and in Pines she's with Hollywood's two heart-throbs, Gosling and Bradley Cooper.
"They are just amazing actors," she says. "It's about the work and they give so much. That's another thing about working with Derek, you know that the cast is going to be stellar and you know they are going to have your back and all the actors did."
The Place Beyond the Pines opens on June 27.
