Leighton Meester is getting old before her time.

The Gossip Girl star, 22, says she has an old head on young shoulders and cannot help being serious and adult even while her friends are running wild.

She explains, “I am mature for my age.

“I guess I grew up fast. But it has helped me. I’ve got my head straight on my shoulders because of that.”Meester was recently reported to be in talks to lead the cast of Screen Gems thriller The Roommate.

She would apparently be playing Sara, a college freshman who is given a dorm with stranger Rebecca. Sara’s friends and family come under threat when Rebecca becomes obsessed with her roommate.

Source: Show Biz Spy