Selena Gomez Parties with Mystery Man at Sundance
updated 01/21/2014 AT 03:00 PM EST
•originally published 01/21/2014 AT 01:50 PM EST
The former Disney darling arrived at the intimate Grey Goose party for her new film Rudderless around 10 p.m. (The singer is getting good buzz at the festival for her portrayal of a grieving college student.) Quickly making her way upstairs, she spent most of the evening with an attractive young man with shaggy blond hair who wore a green sweater.
"She went right up to him really early on in the evening," an onlooker tells PEOPLE of the duo, who were tucked into a corner of the venue close to the stage with several other friends.
Her co-stars (including Billy Crudup) performed a few numbers from the music-heavy film. Meanwhile, Gomez – who wore a cozy beige sweater with an open back and black skinny jeans – sipped on cocktails and chatted closely with her male companion, casually placing both hands on his legs several times throughout the evening. Despite their closeness, a rep for Gomez says the two are simply friends.
New romance or not, Gomez was in great spirits the entire night, standing up to dance along to the music and laughing with her friends and the film's director William H. Macy.
The singer-actress performed two songs at the bash, closing out the evening with an impromptu version of her hit song "Come and Get It" before leaving with her group just after 1 a.m.
Meanwhile, Bieber, 19, spent his Monday night clubbing in Miami.
Bieber visited Mansion in South Beach around 2:30 a.m where "he did not drink and was surrounded by male friends until several girls came to the table,” says a source. "They were club type girls and left with him."
Then it was time to hit the strip club in honor of rapper Lil' Scrappy, who was celebrating his 30th birthday at King of Diamonds.
Check out a clip of Gomez performing at the Sundance bash:
With reporting by LINDA MARX