Leighton Meester is not so nice to her fans, especially the young ones! An insider tells BettyConfidential that the Gossip Girl star and newly minted pop singer isn’t going to have fans lining up to buy her albums and watch her TV show if she isn’t a little more careful about how she treats them.

“Leighton was very rude to young kids backstage at Z100’s Jingle Ball in New York,” our source says. “She didn’t want to take any extra photos with any of the young fans asking for them.”

Backstage Leighton, 23, was heard sighing over the waiting photographers and young people, lamenting her fandemonium. “It’s like this everywhere I go,” she whined. Then one young fan walked up to ask for a special photo and she barely acknowledged the child saying, “No more pictures. I already did pictures.”

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One source, who is familiar with Leighton’s childhood, career and transition to adulthood says, “It’s surprising how Leighton acts now that she’s famous. She and her mom worked very hard to get her to this spot and she could be more gracious. Her mom was her manager and they had very little money and really pushed for Leighton to get roles. She was a very driven child.”

While Leighton ignored excited fans backstage, American Idol runner-up Adam Lambert took every photo request seriously and even helped parents with camera problems as he posed with everyone who asked for a pic.

Magazine and newspaper reporter Kelly Will has written celebrity columns for the New York Times, the New York Daily News and the New York Post. Follow her on Twitter at twitter.com/misswill.