Supergirl and Superman are cousins in the DC Comics universe. However, Kara Zor-El, aka Supergirl, has distinct characteristics that set her apart from her cousin. In interviews, she has mentioned that Superman is overly optimistic, while she sees things more critically. When asked about their relationship, Supergirl said, “He’s a nerd” and added, “I see the truth.” This difference in perception stems from their unique backgrounds and experiences.
Supergirl first appeared in comics in 1959, but it wasn’t until 1984 that she gained widespread recognition with a film adaptation starring Helen Slater and Faye Dunaway. Despite this early success, her legacy has not been as impressive as Superman’s. However, the release of a new Supergirl film offers an opportunity to revisit her character and explore what makes her distinct from her famous cousin.
Source: https://www.wsj.com/arts-culture/film/supergirl-review-dcs-disaffected-heroine-ac671bc6