Place your bets on whether or not this is really happening
Warner Bros. sure has a lot of plans for DC movies: we have multiple movies involving the Joker on the way, a Harley Quinn movie, a Batgirl movie that lost Joss Whedon, and who knows what even else. Warner and DC are adding more to their plate with a Supergirl film, totally reinforcing the DC Films image of trying to bite off more than they can chew.
According to Deadline, screenwriter Oren Uziel is attached to the script; Uziel previously co-wrote 22 Jump Street and was the screenwriter of The Cloverfield Paradox. Uziel also wrote the most recent draft of the script for the live-action Sonic the Hedgehog movie, making his resume quite possibly the weirdest one we’ve seen in a while.
Supergirl, aka Kara Zor-El, had an unsuccessful movie in 1984, spinning off of the Christopher Reeve films. You can see Supergirl on television as played by Melissa Benoist on the CW, so her version of the character will be hard to not think about while watching this movie—assuming it actually releases one day. No start of production date, cast, producers or director were announced, so I’d assume that the studio is waiting to see how Aquaman and Shazam will do first.