Ruby Modine - Lead
Credit: David Crotty/Getty

For Ruby Modine, being cast as Lip Gallagher’s latest love interest on Shameless was pretty much hitting the TV role jackpot. A longtime fan of the Showtime series, Modine was familiar with the Gallaghers’ way of life on the South Side way before landing the part of Sierra, a waitress and single mom who caught the eye of Lip (Jeremy Allen White) the minute he walked into Patsy’s Pies earlier this season. They’ve been steadily hanging out ever since, and after last week’s episode, it looks like things are about to go from casual to serious pretty quickly.

Having followed the trials and tribulations of Lip’s love life since Season 1, Modine is hoping that this time’s the charm—not that she’s biased, or anything. “I just think that they’re really sweet together,” Modine told InStyle after last week’s episode. “There's an ease to them that's very refreshing and nice.” The relationship is certainly different for Lip, who last fell for his married college professor Helene (Sasha Alexander) before getting kicked out of college and heading to rehab. But while working at the diner managed by Lip’s sister, Fiona (Emmy Rossum), what initially began as pure physical attraction between Lip and Sierra has blossomed into something more—and for good reason.

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“I think Lip likes Sierra because she's one of the first people he’s been around that truly has a good attitude,” said Modine. “She knows how to stand up for herself, and even though she has a lot going on, she’s handling it pretty well.” Scroll down for our full interview with the star, and catch her in an all new episode of Shameless on Sunday at 9 p.m. ET on Showtime.

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Credit: Showtime

InStyle: Before Sierra entered the picture, did you have a favorite of Lip’s past love interests?
Ruby Modine:
I did love Mandy a lot, mainly because Emma Greenwell portrayed the character so well. But Mandy encouraged Lip to do well and was really strong. She was just freaking badass. So I would have to say that Mandy was my favorite prior girlfriend for Lip.

Sierra really seems to encourage Lip in the right ways. What do you love about her attitude?
I would imagine that Lip has been so distraught and angry at himself for potentially throwing away the opportunity of going to college, and now he might have another chance—but it seems like he might be too nervous to go back. To have your significant other—or, maybe "significant other" is not the correct term, because they're so casual—but having that support system is important. You want to be with somebody who will encourage you to better yourself and call you out on your crap and be like, "What's the worst that's gonna happen?" instead of encouraging him to play video games and just not think about it.

Do you think Sierra’s positive outlook is what reeled him in?
She’s very playful and definitely calls him out on his ego. He's like, "Are we still keeping it casual? You had me cutting your kid's food and everything," and she throws it back at him. He’s not the end-all be-all, and she has her own life. When she jokingly asked him to marry her and asked why he was fighting this, that was such a moment of her just trying to see how he would react. And the fear in his eyes, that's all that had to be said. Really, I think it's important that he be with somebody that's grounded. And she knows what she wants, which is to protect her kid, to have a job, be stable while also looking out for her brother, although it appears that Debbie is taking over, and Neil seems to very fine and happy with that. It seems like she might become the queen of Neil's house.

Last week, we met Sierra’s ex, Charlie, who abandoned their son when he was supposed to be watching him. Where does Sierra go from there?
I think she’s used to Charlie disappointing her. When she and Lip were playing video games, she explained that her mother kept her away from her father and she doesn't want to do that to her son. She wants to better his life in a way that she wasn't lucky enough to have, and it's really sad. That was a heartbreaking scene to see that Sierra trusted Charlie to take her son and was so nervous about it, and everything she was just hoping for completely fell through. It's awful to be let down, especially by somebody that’s—maybe they're not in love anymore, but they have a child together. I think there's going to be anger and frustration towards Charlie. But because Lip handled it so well and was so sweet about it, Sierra acknowledges that maybe she does have a support system to lean on for the first time ever.

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Will there be a Lip-Charlie showdown?
I think the anger that Lip sees in Sierra, the person he's potentially dating right now, sparks him in some way or another. So I think that the South Side anger we used to see might come up a little bit. And we definitely saw him in the teaser for next week going at it with somebody.

Do you think Lip is ready for a serious relationship and to potentially become a stepdad to Sierra’s son one day?
I think he’s proved that he’s growing quite a lot as the season has progressed. We haven't really seen him drinking much—and he's drinking a lot of water when he does. He's staying grounded at work. He's definitely hustling and doing some shady business to get more money, but he's providing—and I think the sincerity is there.

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Credit: Showtime

You’ve filmed some pretty steamy sex scenes with Jeremy Allen White. What’s that been like?
There's no calm way of answering that. It's great, because he's a great actor. We’re all continuously learning and trying to better our craft, but I can quite honestly say that in my eyes, Jeremy is a master at his craft. He's taught me so much and helped me through so many scenes. He just puts you at ease, and he's been a major anchor with his humor—and even the music that he plays in hair and makeup.

What does he play?
Oh gosh, so much. He plays great music, from old '50s tunes to British hip hop. The hair and makeup trailer is usually quiet until he arrives. You start to hear music and you go, “Jeremy's arrived.” And then he and Cameron will start dancing together, and as you can imagine, Cameron Monaghan and Jeremy Allen White dancing with one another always puts a smile on your face.

What has it been like to work with Emmy Rossum?
Emmy was great since day one. My first scene was when Sierra and Fiona sat down to talk about hiring her, and Emmy truly came from a place of love. She told me, "This is your first time doing nudity. This is your first time in a sex scene, and it was mine as well. I'll give you my number and you can call me, you can text me, and we can discuss it." During one episode that she directed, she pulled me aside to talk about choices that I made, and I appreciate that she did that. Whenever she’s on set, I know that I can go to her and ask her for little bits and pieces of advice. She’s very kind—and also a really good singer! Never in my life did I think I would be on the set of Shameless and watch Emmy Rossum break out into Beyoncé.

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Overall, what’s your favorite thing about playing Sierra?
Being a mom. Lucas is so cute, and the little boy that plays him, Cooper J. Friedman, is such a ray of sunshine on set. But also waitressing. I tried to waitress when I was younger, and it didn't go very well, just because I panicked a lot. I’ve always had the utmost respect for anyone that is in the restaurant business. On the set, we’re running around and bussing tables for so many hours and it feels like it never ends—and we’re not even in the real world. But I do love the new Patsy's uniforms. The suspenders are what really did it for me.