Like a baby bird pushed from the nest by its mother, Allison Williams is taking fashion risks—with the help of her stylist, Thomas Carter Phillips. Last night, for the premiere of her new film, Regretting You, Williams opted for a vampy, vintage raspberry silk one-shouldered John Galliano dress, sourced from LA vintage hotspot, Timeless Vixen.

“I was mostly drawn to the look because of how different it is for me! The silhouette, the material, the color, the design of it…it feels like quite the departure,” Williams tells Vogue. “Thomas and I were deciding between two different things, one much more in my comfort zone…and ultimately, he nudged me outside of it. And I’m grateful for it!”

Williams feels most herself when she’s wearing comfortable clothing. “I think that’s always been the answer, but my willingness to transcend comfort for aesthetics has diminished rapidly as I’ve gotten older,” she says. So what will you find Williams wearing when she hangs up the vintage Galliano? “Soft fabrics with nothing too tight: No constricting bra-strap, ponytail, waistband, shoe, inseam. Life is too short,” she says. “The SECOND I have an opportunity, I’m in Birkenstocks, fluffy grippy socks—my favorite C-section souvenir second to our son—and sweats. Like, immediately. The speed would blow your mind.”

Though she’s most at home in her Birks, that isn’t stopping Williams from raiding her Regretting You character’s closet. “I raided Morgan’s closet. I’m not just saying that because of recency bias; it’s the truth,” she says. “Costume designer Erinn Knight picked such beautiful, wearable pieces that I just couldn’t say goodbye to when we wrapped the movie.”

Here, Allison Williams brings Vogue along as she gets ready for the Regretting You premiere—sans grippy socks.