Supergirl might have made for an interesting film, if done correctly. However, it seems as though they could barely even decide on a genre let alone write a story around this loosely-defined character. Yes, even the comic books can’t tell you who Supergirl is. She must have escaped The Matrix (okay, fine, that wasn’t very funny).
This Nostalgia Chick review also features Linkara from Atop the Fourth Wall. When it comes to comic book characters, there are few people better to ask.