If you’ve been watching Supergirl since its season premiere earlier this month, you know the upcoming “Crisis on Infinite Earths” crossover isn’t the only thing that Kara has to worry about. In addition to the multiverse mayhem that lies ahead, Supergirl is facing some growing personal problems on the home front. During the season 4 finale, Lex Luthor used his dying breath to reveal Kara’s secret identity to his sister Lena. The revelation shocked Lena to her core, since she considered Kara one of her closest friends.

“Once we knew we had Lex Luthor and we had Jon Cryer, it came to us pretty quickly because no one can put salt in a wound for Lena like her brother Lex,” explains Executive Producer Jessica Queller. “That was a really important moment that's going to impact this season tremendously.”

It was an important moment and also a devastating one for fans who have fallen in love with the often-conflicted Lena Luthor since she debuted in Supergirl’s second season. As part of a family known worldwide for their cutthroat approach to doing business, hatred of superheroes and often criminal behavior, Lena has sought to set herself apart from the Luthor name as someone fundamentally different than the people she shares it with. But is she different? Or are those family traits something she just can’t escape, no matter how much she might want to? It’s possible the truth about Kara might finally be the thing that tips her towards the legacy she’s tried so hard to escape. Or maybe not. Lena’s flirted with the dark side before and managed to pull herself back from the abyss. Is it possible she might do it again?

“I think the Lena you see at the end of season four hasn't really thought about it yet,” shares actress Katie McGrath, who plays Lena. “It's just basically trying to survive, and we don't pick up that far ahead in season five. We're about a month later and I think she's still coming to terms with this desperate great deep hurt.”

In other words, fans shouldn’t necessarily expect Lena to turn super-villain…at least not just yet. With an important character like Lena, any spiral into wrongdoing—if it happens—is likely to be a slow burn. But there will be repercussions, even if it’s not clear what exactly they’ll be.

“With around 20 episodes to go, you've got a long journey to plot,” says McGrath. “If you think about it, we're five seasons in and we've been building up to this. It's a huge moment for my character and I don't think I'm stepping out of line saying it's a huge moment for Melissa's character as well. And the idea for me, or for Lena, is what this does to you as a person when you realize that not only your best friend has been lying to you, but everyone. Everyone has kept this truth from you. How that makes you feel separate and how that makes you feel different and treated badly and what that does to somebody and how they move forward from that.”

Considering Lena’s mistrust, if not outright hatred of Supergirl, it’s not surprising Kara took so long to tell her. What was surprising was how quickly she came clean this season. Would it have been any different if she had done that much earlier in her friendship with Lena?

“I think if it had come from Kara first, we wouldn't be having a lot of this storyline,” speculates series star Melissa Benoist. It’s a sentiment that Executive Producer Sarah Schechter clearly agrees with, responding, “We wouldn't have any conflict this year!”

In other words, don’t expect Lena and Kara’s relationship to be like it was before. As Lena herself said in the season five premiere, nothing can ever again be the same between her and Kara.

“The dynamic between Kara and Lena is going to be completely changed,” shares Queller. “Lena's Achilles heel is betrayal, and so the fact that the person she trusted the most, her best friend Kara, has lied to her in this way really devastates her. So, we're going to be battling for their friendship and see if it can recover.”

Like her brother Lex, Lena’s reaction could potentially have world changing consequences that go beyond her personal relationship with Kara.

“In typical Luthor fashion, she doesn't decide to go to therapy, she decides the answer is she's going to save humanity,” reveals McGrath “Because we don't think small! Luthors dream big. That's where she's at. It's this idea that when everything you know has been taken away from you, how do you stand back up and keep going? That's what she does. No matter what you do to her, she keeps going. She's moving forward.”

We can only hope it’s not in her brother’s footsteps.

Supergirl airs Sundays at 9 p.m. (8 p.m. CST) on The CW. For all the latest Supergirl news, features and conversation, click here.