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You’d be forgiven for assuming that Sharp Objects director Jean-Marc Vallée got his hands on some miraculous de-aging technology for the scenes where Camille Preaker (Amy Adams) flashes back to her younger self. Instead, the HBO mini-series found a dead ringer for Adams herself in Sophia Lillis. The 16-year-old actress, who starred in last year’s It, has made something of a career out of playing the younger version of Oscar-nominated Hollywood redheads, since Jessica Chastain will play the older version of her It character in the upcoming sequel. As Sharp Objects unravels Camille’s backstory, Vulture talked with Lillis about the prosthetic nose that turned her into Adams’s double, learning to roller skate for the show, and what it’s like to play Nancy Drew.

When you were in It, a lot of people suggested Amy Adams should play the older version of your character. What’s it like for that to actually happen?

It’s amazing to play her. I mean, I’ve heard before that she kinda looks like me, and I decided earlier that it was either gonna be Jessica Chastain or maybe Amy Adams to play my older self for It. But I got to play Jessica Chastain’s younger self and Amy Adams’s younger self.

It can be Bryce Dallas Howard next. Or Isla Fisher.

I’m not really a redhead, but I keep playing these redhead actresses. Which I don’t mind, I think it’s fun.

Do you have a favorite Amy Adams or Jessica Chastain performance?

Junebug is my favorite Amy Adams movie. I remember watching Mama a lot. I watched it because Andy [Muschietti, who directed It] shot it. Actually, when I was in acting class, my film teacher really loved Andy’s short film of Mama. Almost every day, he’d show it to us. Every day, since I was 7, I kept seeing his short film. Years later now, I worked with Andy and was like, “I saw your short film a lot.” I went over to the see the full-length movie, of course, and that was the first thing I’d ever seen Jessica Chastain in. I’d heard that she looked like me, and she might play me, and I thought, “I would love for her play the older me.”

I’d heard you used a nose prosthetic so you’d look more like Amy Adams. What was the process like for that?

She has a more pointier nose, so they took a mold of her nose and then put it on me. But it changed over time. It also seemed to get a little smaller the more time we did it, so at the end, it just looked like a subtle bump.

Did you have to learn to roller-skate for Sharp Objects?

When I first started acting, I knew that you have to learn different skills for different roles. There’s a lot of skateboarding in Nancy Drew. Now, with this one, I had to roller-skate. I’ve always wanted to roller-skate, actually, but I never really thought of it until I got this role. I really had to learn how to roller-skate. I think I improved. I know I can stay on it. I’m thinking about doing it more over the summer.

Jean-Marc Vallée is known for having a distinctive style of filming, and trying out a lot of different things on set. What was it like to adapt to that?

It was very fun, but he is kinda eccentric. He does do that a lot. While we’re shooting, he’s like, “I’ve got an idea. Why don’t we do this instead?” He made us run through a field, and as he goes, he finds different things to do and different ideas that he wants to try out. Which is very good.

In the first episode, a scene cuts from Amy Adams in a bathtub to you emerging from the water in a swamp. How did you shoot that?

They made that [swamp], so it was less gross. Jean-Marc, at the very beginning, showed me the swamp thing I was gonna get into, and he ran in there, because he had to be in there with the camera to see what it’s like. I didn’t know how to react at first. I’m like, “Well, I guess I’ll go in, too.”

One thing I learned about Jean-Marc is that he’s very good with kids. He’s very nice to the kids, especially. The first time I ever talked to him, he said he likes to tell you what’s happening in a scene, and then he just lets the actor do what they want. On the spot, he says, “I’ll see what happens. If I like it, I like. If I don’t, I don’t.”

During a flashback to her sister’s funeral, Camille breaks down and tries to rub the makeup off of Marian’s corpse while Adora holds her back. Tell me about shooting that.

Patricia Clarkson, man, she’s good. I was a little nervous, for sure. I was acting with all the other adults and everybody was there. It was my first scene with all of them, so it was a little nerve racking. But Lulu [Wilson, who plays Marian] made me relax a little bit. She’s a very funny person, and she told me that she’s very used to playing dead in her past roles. All my nervousness was built up, so it was a little easier to do that scene. It’s very therapeutic to let all your nervousness out, you know?

With It and Sharp Objects, you’ve done these two very intense, horror-filled projects. Was it tough to shift gears into Nancy Drew?

It is very different, but refreshing. Even so, Nancy Drew, in the books, her mom is dead. I’m still in that kind of role, it’s just a little less intense, you know? It’s very different from what I’m used to playing, but I’m really happy I got to play her. It’s good to have a variety.

This interview has been edited and condensed.