However annoying your roommates might be, it’s a safe bet they’re not as trying as Leighton… However annoying your roommates might be, it’s a safe bet they’re not as trying as Leighton Meester’s character in “The Roommate.”

The film opens this Friday, starring Meester as Rebecca, a deranged college freshman who develops an unhealthy obsession with her roommate, Sara (Minka Kelly). Rebecca, who has a history of mental disorder, seems normal at first, but soon regresses into insanity and becomes a danger to those around her.

The role is a big departure for Meester, who is a series regular on the hit show “Gossip Girl.” Nevertheless, Meester, who also stars in “Country Strong,” said she was up for the challenge. In a conference call with several college publications, Meester discussed her role and the difficulties it presented.

Question: What kind of an impact did playing Rebecca have on you?

Leighton Meester: I can’t say it wasn’t fun — it was — but it was also intense, I think for everyone… [To] try to share something in common with her or try to understand her motives and relate to her in some way, it was extremely difficult for me to do that with her, starting off, because [of] how she unravels. Some of the things I had to do were really disturbing to me — particularly a scene involving a kitten.

Q: This was your first thriller. What was it like to play the villain?

LM: It was scary. I was genuinely scared at points, but it’s sort of funny that I’m what’s scary in the movie. I’m really proud of it and how it turned out. I can’t say that I wasn’t at all affected by it — it stays with you a bit if you’re terrorizing people all day.

Q: How did you prepare for your role in “The Roommate?” Did you talk to psychiatrists about the condition of your character?

LM: I was really lucky I had the opportunity to really prepare for this. I got a lot of really great psychology books and information on delusion [and] mental disorder, especially in women, and I had the chance to speak with different psychiatrists about the disorder. The psychiatrists I spoke to I think were the most helpful because they would describe in gross detail different cases they worked on defending.

Q: What would you be looking for in the perfect roommate?

LM: I actually love living alone. I used to have roommates all the time and it’s a challenge to live with people. Someone who’s clean I guess. I lived with all different roommates and there was always parties going on whenever I came home and you’re sort of expected to socialize all the time, even when you don’t want to. For the most part I was pretty lucky, but I have had some not-so-good experiences with female roommates who eat all your food and take all your clothes.

Q: How was this role similar and/or different from your role as Blair on “Gossip Girl”?

LM: It couldn’t have been more different. The character, she is from a different place, she has a different background [and] different parents. Rebecca has a history of having mental disorder. It’s not at all the same as what I play day to day on my show, [it’s] a pleasure to break from that and do something different, but it’s also so incredibly different from who I am as a person.

Q: What attracted you to this particular script?

LM: The character. I love to break down and see where I can relate to somebody and find the humanity in them. I want to care about my character and love my character [but] it was not easy with Rebecca. If you track her actions, they’re always motivated by something internal and obviously not based in reality. It’s a subject that most people can relate to. It’s about friends and it goes terribly wrong because one person is really invested in the friendship and becomes unhealthily attached. I think a lot of people have been there — probably not to this extreme, but I know that I’ve had friends that are just a little bit too nosy, needy, in your space and in your business.