Brad Pitt and Ines de Ramon Plan on Spending New Year's Eve Together: They're 'Happy': Sources

Kurt Krieger/Corbis via Getty; Alberto E. Rodriguez/Getty Brad Pitt; Ines de Ramon

Brad Pitt and girlfriend Ines de Ramon have their New Year's Eve plans made.

After the Oscar-winning actor, 58, was seen with the jewelry executive, 32, at the afterparty for his new movie Babylon Thursday night, a fashion industry source close to de Ramon tells PEOPLE that Pitt "is clearly very into her given he brought her to his premiere."

"Ines said that Brad is very sweet," the source says, noting that the pair "are planning to spend New Year's Eve together."

Meanwhile, a source close to Pitt tells PEOPLE the pair are "dating and happy," adding, "It's not serious yet but he's comfortable and they're having fun together."

A separate insider says Pitt "enjoys dating Ines" and they "hang out when they are not busy." The insider adds, "Ines is fun and social. They have a great time together. They do solo dates, but also group dates with friends."

RELATED: Brad Pitt Mingles with Girlfriend Ines de Ramon at Babylon Premiere Afterparty

Jim Spellman/Getty; Michael Tran/AFP/Getty

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The couple's outing at Thursday's Babylon premiere comes a month after PEOPLE confirmed the pair "have been dating for a few months." They were first photographed together on Nov. 13 alongside Cindy Crawford and Rande Gerber backstage at a Bono concert at Los Angeles' Orpheum Theatre.

According to a source at the time, "Brad is really into" de Ramon, who separated from her husband, Vampire Diaries star Paul Wesley, earlier this year.

Speaking to PEOPLE Thursday on the Babylon premiere red carpet, Pitt described the "intense" production of the over-the-top 1920s film, which also stars Diego Calva, Tobey Maguire, Olivia Wilde, Jean Smart and Pitt's Once Upon a Time... in Hollywood costar Margot Robbie.

"We have 700 extras, doing a war scene in the background. We're trying to catch it right when the sun goes down," Pitt said.

"That's really what movie-making feels like," he added. "You're losing the light, everyone's racing, jamming, to try to get this thing just right and we've only got this window of time and that's it. It's locked into cement. It's intense. So there's a moment of that in the film that's really beautiful."

Babylon is in theaters Dec. 23.