AceShowbiz - Leighton Meester's castmates on the set of upcoming movie "The Roommate" were convinced the actress was "antisocial", because she completely isolated herself to prepare for the disturbing role. The "Gossip Girl" star plays a deranged student in the thriller alongside Minka Kelly, Billy Zane and Cam Gigandet.

Meester used a number of acting techniques to add realism to the role and she locked herself away in her trailer for long periods of time to perfect her portrayal of the loathsome character. She tells Nylon, "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."

And even her co-stars noticed her odd behavior - Kelly adds, "People on set would mistake her for being sort of antisocial. She would isolate herself from everyone." "The Roommate" is due for release in the U.S. next week.