'Supergirl' last left off with Lena Luthor learning her employee Sam was the Worldkiller, Reign.

But some other secrets may cause friction with Lena and Kara.

The show's co-showrunner Jessica Queller said it sets up a triangle between the friends that makes it "challenging" for Kara and her super identity.

Lena has a very different relationship with Kara Danvers than she does with Supergirl...