"It's been a really long time," she told PEOPLE at a luncheon thrown by the Diamond International Corporation in her honor. "It's kind of nostalgic now ... I think I'm just gonna remember this weekend really vividly forever."
The best actress nominee, who glowed in a yellow sun dress by Bottega and jewels from DIC's Everlon Diamond Knot collection (3.25 carat drop earrings by Fred Leighton set in 18 carat gold and silver), says the best thing about award season is getting to spend time with the cast and crew of the film that's made her a star. "I've never done a job before where I got to spend that time after it with [the cast]," she says. "That's been my favorite part. I go to different cities and travel with all these people. We all got on so well."
Mulligan adds: "I'm really just trying to enjoy it. I want to let these last three days be savored."
In fact, costars Peter Sarsgaard, briefly joined by wife Maggie Gyllenhaal, and Olivia Williams stopped by to help her celebrate. But meeting one of her idols face-to-face is still a highlight. Take Daniel Day-Lewis, who she calls "the most incredible actor on the planet but so lovely." She admits the Nineactor leaves her star struck – even though they share an agent and see each other from time to time!
"It's really comforting to see how normal and grounded everyone is," Mulligan says. "When you're around these people for a whole season, these incredible actors that you've looked up to your whole life, suddenly they start to become very human. They reach out to you and they're friendly ... Some of the most amazing actors are so sweet and kind. You just never expect that from people, real friendship and warmth."
She'll be joined by her parents and her brother at the 82nd Annual Academy Awards Sunday, which will be televised live on ABC beginning at 5 p.m. PT/ 8 p.m. ET. Curious what she'll be wearing: She says, classic with a twist. "It's the last weekend of this whole journey, so we can just sort of enjoy it now," Mulligan says. "I want to!"