Similar to how fans thought it was odd to have a Flash movie when there's a CW series based on the character, we're now getting a Supergirl movie even though the Melissa Benoist show is considered a success by many. There's nothing wrong with new interpretations and there are people who like Ezra Miller's Flash so we can only hope that this version of Supergirl is just as likable.
Unsurprisingly, Warner Bros. is hoping to get a female director for the movie. No potential options have been named yet, according to Deadline but that will likely change in the coming months.
Due to the current landscape, it seems like fans want more diversity in their films, hence the search for a female director for this DC movie. This isn't a bad thing at all but let's hope that they choose a director for their film quality and not just because they're female. Admittedly, it worked for Patty Jenkins and Wonder Woman, so let's hope for good things.
It's likely that the film will be set in the DCEU so this version of Kara could interact with Henry Cavill's Superman. There was also a Man of Steel prequel comic that showed Kara surviving the explosion of Krypton, so the film can base Kara's origins on that.
Supergirl currently has no release date.