Imogen Poots
Imogen Poots is a British actress starring in I Kill Giants, Filth, Fright Night, and 28 Weeks Later. She has starred alongside some big names yet is never drowned by them. A role like Supergirl is challenging and needs an actress who can hold the movie together.
Imogen has shown in movies such as Filth she is able to outshine actors with bigger roles. This is a quality any actor needs in order to lead a successful franchise.
There are no qualms in her ability to play the Earth-based Kara Danvers persona. The hard-hitting Supergirl is where she could surprise everyone, though.
Casting her is sure to make fans happy. Her name next to Supergirl in a browser search shows more than a few websites where she is at the top of lists to portray the character.
This was true even before the confirmation of the movie.