The 17-year-old star was seen "literally jumping and dancing" at the bash alongside superstar pals Taylor Swift, Jaime King and Sarah Hyland.
"Everyone was really into it," an eyewitness told Us Weekly of the ladies. "Taylor was basically dancing as if she was at a heavy metal concert and loving it."
"They were dancing hard," another source added. "Taylor had a flute of Moet [& Chandon champagne] in her hand and was dancing and singing along to Def Leppard's 'Pour Some Sugar on Me.' Jaime King and Taylor were grinding along to the song, facing each other, but not in a sexual way."
The insider claimed that the girls were the life of the party and that Twilight star Peter Facinelli and his pals couldn't take their eyes off of them.
The Romeo and Juliet star reminisced of her fun night Monday, posting a picture of her with her friends on Instagram.
Steinfeld is best known for her role as Mattie Ross in the 2010 film True Grit which earned her an Academy Award nomination for Best Supporting Actress and a BAFTA Award for Best Actress in a Leading Role.
Swim Week Miami Beach 2014 [PHOTOS]