Should a parallel world exist, and Blake Lively exist within it, her life might look a little something like this: she's a chef at a hip, low-key diner in a bustling town, constantly reinventing a menu, and creating dishes that are served up by waiters who could seamlessly slot into a high-fashion campaign.

For now, though, this world seems perfectly content with the Blake Lively it has. Having broken out in 2005's tween flick The Sisterhood of the Traveling Pants, two years later, Lively snared the role that would make her a household name: playing Upper East Side Manhattanite Serena van der Woodsen in the TV series Gossip Girl.

While Gossip Girl airs its last season from October 9 (on FOX8), Lively has a guaranteed future on the big screen. This month, Lively follows up turns in The Private Lives of Pippa Lee (2009), The Town (2010), and Hick (out on DVD September 26), with another edgy role, this time in the Oliver Stone-directed thriller, Savages.

Your part in Savages was obviously a very gritty role for you—and not your first tough film role. Why do you choose these parts?
"It's funny. I thought that I just liked to choose complex women [to play], but then I realised that the women I played in the last three movies were drug addicts who also had a lot of sexual issues! I always look for something that's challenging. I like to feel like I can't do it, and at the end of the day, if I made it through the four months [of filming], that's the reward for me."

You had some difficult scenes to perform in Savages. Even watching it isn't that easy at times! How did it feel to be so vulnerable?
"It was a very vulnerable position to be in, for the character and also personally. Oliver [Stone] is a very strong, intense man who's always pushing you to the limit, always pushing your buttons. You know you have to do these scenes that are raw and exposed. It's terrifying! The only solace is that at the end of the day, Oliver will make a great film. You just have to trust that even though you're terrified to be doing these things, it is going to turn out well."

You're considered a style icon, but are there certain trends you just won't wear?
"I don't know, it just has to feel right. There are a lot of things that I see on other people that I love, but I would never put on myself just because it wouldn't look good. I think the most important thing is to feel good. That's something I learned young."

Is there any one standout piece that you have been able to snare from the set of Gossip Girl?
"It's the first piece that I saw [while filming] Gossip Girl—a Gucci handbag, embroidered, with a bamboo handle wrapped in leather and rose-gold details. It was so beautiful that I said to the costume designer, 'Oh. I can't imagine…do you think one day I could buy something like that?' She called Gucci, came back and said, 'They said you can have it.' It's still one of my very, very favourite pieces."

You seem to always get it right on the red carpet. But have you ever made a fashion faux pas, maybe looked at a picture of yourself at an event and asked, 'What was I thinking?'
"I think the biggest faux pas is to actually look at the picture, you know? Things always photograph differently and it's about how you feel on the night. It's walking out the door and [thinking], 'Ah, I feel great about this.' Why would you go home and be like, 'Oh no. That's what I look like?' Why ruin the illusion?"

For the full story, check out the October issue of InStyle, on sale now