Kryptonsite’s got the casting breakdown… notice they don’t say tall!
SUPERGIRL” (Kara) – 19 years old, Caucasian, blonds preferred, or willing to dye hair blond. Beautiful, smart and funny. She is Clark’s cousin. She was born on Krypton and is the daughter of Zor-El, Jor-El’s brother. Kara possesses all of Clark’s power and one he doesn’t yet have – she can FLY! Kara also has a strong, rebellious streak which puts her at odds with Clark, and puts her into Lex’s radar. This is a 7/13 Series Regular role.
Sounds like a great fit for Kristen Bell to us… if the unthinkable really does happen.