is taking inspiration from a classic Superman story for episode 13. One of the most famous Superman stories is called "For the Man Who Has Everything" and it involved Clark Kent getting to live out his fantasy life on Krypton where his family never died. As you can imagine, "For the Girl Who Has Everything" is essentially Kara being cast in Clark's role.
The Supergirl budget clearly can't afford for the entire episode to be set on Krypton. While Kara being stuck in a dream-Krypton is still an aspect of the episode, the focus is on the friends and family left behind. It's very easy to argue that for episode 13, Alex is the main character, not Kara. Alex has always been an enjoyable character but never that essential. In "For the Girl Who Has Everything," Alex and actress Chyler Leigh really steps things up and it's honestly amazing.