Supergirl will feature Kara Zor-El, Superman’s cousin, and is planned to have the character in full super form. She’s had her powers for years and is now, in the series, at age 24, embracing them and her responsibility to be a hero. Here's the official description:
Born on the planet Krypton, Kara Zor-el escaped amid its destruction years ago. Since arriving on Earth, she’s been hiding the powers she shares with her famous cousin. But now at age 24, she decides to embrace her superhuman abilities and be the hero she was always meant to be.
Berlanti and Adler are writing the pilot script, and Geoff Johns is “closely involved.” As CCO of DCE, he has been involved in all of their recent TV success
No timeline has been given for the TV series’ pilot production or its possible premiere.