The leaker claims to be friends with the artist who was contracted to create concept art of the actresses as Batgirl, and then shared them with the leaker.
The leak also claims that Warner Bros. wants to reveal the actress in a surprise announcement at San Diego Comic-Con next month, which makes sense but who knows?
A list of actresses who are under consideration to play the lead in Batgirl was posted to the Reddit sub-group DCEU Leaks.
Apparently, these four actresses are the frontrunners for Batgirl.