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Leighton Meester is a single Gossip Girl once more.

A source close to the 24-year-old actress confirms to that she has broken up with actor Sebastian Stan, 26, her boyfriend since 2008.

"They are still friends," the source tells Us. "It was amicable. They still talk all the time."

Meester and Stan met -- and made out -- on the set of her show Gossip Girl, where Stan occasionally guest-stars as Carter Baizen.

For Valentine's Day 2009, they enjoyed a couples' retreat in Jamaica with fellow Gossip Girl pair Jessica Szhor and Ed Westwick.  Last October, Meester gushed to Buzznet about a romantic gift -- a painting -- from Stan, whom she called her "best friend" and "boyfriend."

"He told the artist about me, my favorite colors and poetry and she painted a large very special abstract work I have hanging in my dining room," she said.