I met up with Steffy on a Sunday, her least favorite day of the week. “I hate Sundays. Maybe I’m work-obsessed; I love to work. Work, work, work. I don’t know what to do—I’m a mess when it’s a Sunday.” Maybe she’s a mess, but she’s a perfect mess: her ensemble consists of a grunge-era flannel from What Comes Around Goes Around, her mother’s shredded Diesel jeans from the 80’s, a vintage Fendi mink, a fur-trimmed Prada beanie (“I found it in St. Tropez, of all places!”), a black Hermès Kelly and several Repossi rings. The girl gives new meaning to high/low. It’s no wonder, then, that she’s Olivier Theyskens’ lucky charm: his muse and design assistant at Theory. I spotted her days earlier, shopping at the Alexander Wang boutique in SoHo, and practically shouted, “Who is that???” to no one in particular. The grown-out, lopped off, messed up hair just looked so good. And then there was that little bit of second-day smoke around the eye—the kind you hope to wake up with even though you took it off the night before (or not…). And when I say hi and she says hi, it’s with a French accent. OF COURSE.

“I love to dress, but makeup—I am terrible at it. Skin…I clean my skin, but I’m not very—how do you say it? You speak French? I use like, Avène or La Roche Posay, La Prairie, or—and then when it’s finished, I do something else. I didn’t find the right thing yet, and there’s so many brands—I don’t know what to pick. I just clean it in the night with cleanser, or makeup remover. I use a Sisley cleanser now because the woman who did my facial recently here in New York, at the Carlyle spa, they use Sisley—and I kind of like that. The thing I use the most is Hydrance Optimale cream by Avène. It’s super simple. And when I get spots, I’ve stuck to this one thing since I was a little girl— Dr Christine Schrammek Blemish Balm. You put it on, it dries it up, and it’s gone. It’s really good. For makeup, my sister and my mother just told me, ‘Wear makeup!’ and I bought everything from Chanel. Actually, a very nice lady at the Chanel counter—she told me I should wear Vitalumière Aqua foundation, and some eye shadow, and eyeliner, but the most time, I’m not wearing anything. It’s very good, but I don’t use it—the only thing I use is a little dark eye shadow with a brush, around the eye, like eyeliner. I think it looks ugly when you see a precise line—it’s too obvious. And then what I like is a red lipstick. I love it. The Cruella, I love this from NARS. I have Venise from Chanel, I wear a lot—amazing. That’s basically it. I cut my hair, it was very long. I really like this guy’s products, Christoph Robin—the lemon cleansing cream. This is how it looks so greasy… I like it when it looks dirty—I hate it when I’ve just washed it! [Laughs] I did my color at Christoph Robin, but before I was with Remy at David Mallett. I’m not very particular, sticking to one place—I change all the time. I have five tattoos…I told myself I’d stop at five. It’s dangerous—once you start. My sister’s name, Gigi—which I got at New York Adorned, by the way; a ladybug, because I am naïve and it brings luck in a way; ‘no guts no glory,’ which is my life’s motto. I want to take risks in life—and it’s like, have the guts, or somehow you won’t succeed—so just go for it. Most of the tattoos, and the ear piercings, are just on the left side of my body—the right side is all very pure. I don’t want to overdo it. It’s very hidden, and it’s very primitive.”