Jennifer Lawrence has a lot more to say about the gender pay gap in Hollywood.

The "Joy" star made a surprise appearance at the Ninth Annual Women in Film Pre-Oscar Party -- presented by Max Mara, BMW, M.A.C. Cosmetics, FIJI Water and Perrier-Jouët -- at Hyde On Sunset in West Hollywood, California, on Friday, where she was all smiles while continuing her fight for equal pay.

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Dressed in a Dior Haute Couture embroidered off-white wool jacket and a black knitted silk dress, the 25-year-old actress took the stage with Women In Film LA president Cathy Schulma. Lawrence spoke right after Patricia Arquette gave a speech about her change.org/era petition, which was created to urge lawmakers to vote to ratify the Equal Rights Amendment.

An insider tells ET that even though Lawrence delivered her impromptu speech flawlessly, she was a bit hesitant to go onstage at first.

"I'm a huge fan of Patricia Arquette," she explained to the crowd. "I actually played the younger version of her [on the crime show "Medium"]. I love that she stood up, for starting a conversation. We're getting dialogue going. I'm going to go home, and I'm going to go to change.org/era ... I'm going to that. Let's all do it."

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She concluded her speech with a chant: "Equal pay, woo!"

The star-studded event honored all 51 women who have been nominated for an Oscar this year, both in front of and behind the camera, including Alicia Vikander, Charlotte Rampling and Jennifer Jason Leigh. Other stars in attendance included Alicia Silverstone, Michelle Monaghan, Sasha Alexander, Diane Warren, Maria Bello, Lake Bell, Carrie Preston and Maggie Grace.

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Last October, Lawrence penned an essay for Lena Dunham's newsletter, Lenny Letter, in which she addressed her experience with pay inequality in the film industry following the Sony hack. A number of celebrities have already showed their support for the well-written piece, including Julia Roberts.