Lively began her acting career at age 11, when she appeared in the 1998 film Sandman, which was directed by Lively's father. Lively describes her role in the film as having been a "bit part". After not having any involvement with acting for almost seven years, Lively appeared in the film adaptation of the novel of the same name, The Sisterhood of the Traveling Pants in 2005. Lively, appearing with America Ferrera, Amber Tamblyn and Alexis Bledel, played Bridget, one of the four female leads. Lively's performance in the film earned her a nomination for a Teen Choice Award for "Choice Movie Breakout - Female." With a box office revenue of $42 million, the film was Lively's biggest commercially successful film until it was out-grossed by its sequel.
In 2006, she co-starred with Justin Long in Accepted, and Lively, along with her older siblings Robyn, Ernie and Lori, had minor roles in the horror film, Simon Says. While Accepted wasn't well received by critics, Lively's performance was, earning her an award from Hollywood Life, in the category of 'Breakthrough Award'. In 2007, Lively played one of the two title characters in Elvis and Anabelle as Anabelle, a bulimic girl who hoped to win a beauty pageant. Lively said of getting into character for the role that she'd 'shed serious weight' for her height. Lively recalled that: "Beauty queens are still very toned [...] So I lost weight, but I got toned. It was the healthiest I’ve ever been. I just made chicken breasts from Whole Foods on a George Foreman Grill, with asparagus and broccoli.” Lively stated that that process was difficult for her because food is “the No. 1 love of my life.”MovieLine.com praised her performance in the film and credited it as having been her "breakthrough role".
Lively was cast in the CW's series Gossip Girl which premiered in September 2007. She plays Serena van der Woodsen in the teen drama. While rumors of infighting among the Gossip Girl co-stars have circulated in the tabloids, Lively denies that there is any unfriendly competition on-set. “The media is always trying to pit us against each other," she said, "I guess because it’s just not interesting to say, ‘Everyone gets along; everybody just works 18-hour days and goes home to sleep.’ That’s not fun to read, I guess.” Her first magazine cover was the November 2007 issue of Cosmo Girl, where she discussed her time in high school and her career prior to Gossip Girl.
In 2008, Lively, along with Ferrera, Bledel and Tamblyn, reprised their roles in the 2008 sequel, The Sisterhood of the Traveling Pants 2. Similar to the first film, Lively, her three costars and the film were positively received by critics.[As of November 2009, the film had earned over $44 million at the box office, taking in slightly more that its predecessor and thus becoming Lively's most commercially successful film to date. In 2009, Lively appeared as Gabrielle DiMarco, a minor role in the romantic comedy, New York, I Love You, a sequel to the 2006 film Paris, je t'aime consisting of an ensemble cast, . The ensemble cast included Shia LaBeouf, Natalie Portman, Hayden Christensen, Rachel Bilson, and Orlando Bloom. Similar to the film's predecessor, the film is composed of short films along the theme of finding love. Despite positive reception from critics, the film had a poor box office performance.
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