One of the most interesting discussion points among many Supergirl viewers leading into the finale is the notion that sooner or later, Lena Luthor is going to have to learn the truth about Kara Danvers being Supergirl. When she does find out, there is in turn this presumption that there will be hell to pay.
Is this actually the case, though? The real answer there may be a little bit more complicated, given that there is something interesting about having the secret still out there. It’s like when there was Patty Spivot on The Flash, and you had someone who interacted with Barry Allen who didn’t figure out who he was until right before he left.
“Part of the fun is the fact that she’s one of the only people who doesn’t know, and that gives their relationship something different than she has with anybody else. With Lena, Kara can just be Kara; she can be Kara Danvers, not the superhero. She doesn’t have this weight and this responsibility on her. All she has to do when she’s with Lena is be a good friend. So I hope you, in a way, never see it, because what you have between the two is a very equal relationship. Lena doesn’t have to be this powerful corporate leader, she can just be a flawed human being, and so can Kara. The longer that you don’t ever see that, to me, the better.”
One of the other primary reasons to keep this reveal a secret for season 3 is rather simple: Anticipation. The longer that Kara and Lena are friends, and the longer in turn that the secret about the two of them does not come out, the more likely it is that there will be a catastrophic rift when it does that could devastate and sever the friendship in a way that makes it hard to repair. If Lena ever does turn evil, feeling betrayed by a close friend could be a good reason why.