(Cover) - EN Showbiz - Leighton Meester prepared for her new movie by spending hours alone in her trailer.

The actress plays a college student who becomes obsessed with her new friend in The Roommate. In order to get into the character of deranged Rebecca, Leighton locked herself away and avoided spending time with the cast and crew.

I spent a lot of time listening to music that made me feel a certain way, and I started staring in the mirror and not liking myself," Leighton said in an interview with the February issue of Nylon.

Fellow Roommate star Minka Kelly who plays Sara, the girl randomly selected to share a room with Rebecca at college admits she was totally convinced by Leightons performance in the movie. She has revealed some people misunderstood Leightons dedication to the role as her being unfriendly, but Minka was quick to set them straight.

"People on set would mistake her for being sort of antisocial. She would isolate herself from everyone, Minka explained. She worked with psychologists; she really studied the illness of the character, so much that at times on set I was a little concerned whether or not she was there because she scared me so much! The look in her eye was so surreal I was in awe at how much she committed to it.

During the interview, Leighton also spoke about her role in Gossip Girl. The 24-year-old star plays spoilt New York socialite Blair Waldorf in the popular American television show and Leighton has confessed she is very different from the conniving character she plays.

Blair is... I don't know what she is... I have to enter a completely foreign body to sympathise with Blair and her decisions, Leighton added. Blair is very competitive and conniving, and it obviously comes, usually, from a very human place, but she makes decisions that I would never make. (C) Cover Media