Cheryl Blossom is the ruthless queen bee of Riverdale High. She's the captain of the River Vixens, the most popular (and hated) girl in town, and a master of manipulation. She's also completely miserable.

It would be easy to write Cheryl off as little more than a direct disciple of mean girls Heather Chandler and Regina George, cold and calculating and drop-dead gorgeous. But on Riverdale, the school's "bereaved red widow" has more bite than that. One minute she seems genuinely devastated over her twin brother Jason's murder; the next, it appears as though it's all one masterfully executed facade. That's what makes Madelaine Petsch's performance so delightful: you never know what Cheryl's going to do next. Will she break, or clap back with an astutely merciless pop-culture witticism?

In tonight's episode of Riverdale ("Body Double"), we get a little of both. Cheryl makes a shocking confession about her brother's death, one that paints a picture of a "broken little girl who lost the love of her life," Petsch tells MTV News. She'll also have a chance to start anew with her favorite punching bag, Betty (Lili Reinhart). MTV News has the scoop in our interview with Petsch below.

Cheryl is such a fascinating character because on the surface she's a "stock character from a ’90s teen movie," as Veronica puts it, but there's more to her than that. One minute she's ruthless and the next she's crying in the locker room. Do you think of her as an antagonist?

Madelaine Petsch: When I got the audition, it said, "The villain." So that's what I originally walked into it thinking, but when I read the script for the pilot, I realized that she's just this broken little girl who lost the love of her life: her brother. She doesn't know how to navigate through these waters alone, so she just lashes out at people for no apparent reason other than the fact that she's miserably alone. Her family and her have a terrible relationship. She doesn't have any friends; her only friends are Ginger and Tina, who are ready to walk over her at any moment to get where they want to be. So she's just really alone. She feels like she's in charge, but in reality everyone hates her.

And she's incredibly vulnerable.

Petsch: That's why she takes every moment she can, like that moment with Veronica, where she can be consoled by that person, but it's also embarrassing to her because she's so used to being the queen bee. Now that this is happening to her, she's embarrassed. It's a very embarrassing time for Cheryl — and it only gets more embarrassing from here.

Cheryl is obviously heartbroken over Jason's death, and as much as the show is trying to convince us that Cheryl is the killer, I don't buy it. She loved her brother. But maybe she didn't know her brother as well as she thought she did?

Petsch: Cheryl stands behind everything she's ever said about Jason. As creepy as their relationship was, it was real. She truly loved him, and he's the only one that has ever shown her any sort of real love before. She thought the world of him. He was the golden boy. But that facade is going to start breaking down, and breaking her down, as some of Jason's impurities come to light.

And the ongoing mystery surrounding his death is the arc of Season 1?

Petsch: Yes! That mystery will be solved by the end of the season. We're all dying to know. Roberto [Aguirre-Sacasa], the showrunner, teased that we were going to shoot alternate endings so that no one would know who really did it.

Cheryl gets some of the best one-liners on the show. She also talks incredibly fast. Was it difficult to find that rhythm at first?

Petsch: That was a character choice for me. Cheryl's going a mile a minute all the time. I have a different voice for Cheryl, too. She's very manic when her facade is on, and then when she's broken down, and she's in that vulnerable place, she's more grounded.

That scene between Cheryl and Veronica, with Betty watching from a distance, was one of my favorites in Episode 2 because this is a show that really celebrates female friendships. Those moments are really powerful. Even when Cheryl is at her worst, you can see why she's doing it. She just wants friends.

Petsch: Absolutely. You can see that in the amount of times I pop up randomly in the main gang. Cheryl always shows up unexpectedly and unannounced, and that's because she wants to be a part of that. She doesn't go about it in a regular way. She's not being nice and asking to hang out; she's crashing the party. She ends up getting snippy because she wanted to be included. She feels like she doesn't belong anywhere, but in reality, if she sat down with them and said, "Hey, guys, I don't have any friends, and I want to hang out with you and get to know you," I guarantee you that every one of those four would say, "Absolutely, Cheryl. Let's get to know you."

Cheryl and Betty have a complicated relationship. Cheryl loves to tear Betty down. Do you think she does that because maybe she's jealous of Betty?

Petsch: Cheryl is not the good girl, and she's never been seen as the good girl. Betty is the antithesis of that, and Cheryl finds that very fascinating. She wants to see how hard she can push Betty until she breaks, so she can say, "See? Nobody's perfect." But Betty never breaks — until that moment when Betty tells Cheryl to get the fuck out of her house. I think Cheryl really likes that. She's scared for her life in that moment, but she also appreciates the way Betty went about it. She just wants Betty to stand up for herself.