[Annuga]

I haven't seen Gotham City Sirens get mentioned. Here's a part of the movie on Wikipedia

It was announced in December 2016 that Warner Bros. are developing a spin-off film adaptation of Suicide Squad based on Gotham City Sirens. The film is being fast-tracked into production, and will be a part of the DC Extended Universe. Margot Robbie will reprise her role as Harley Quinn and will executive produce the film. Suicide Squad director David Ayer will return to direct the film, while Geneva Dworet-Robertson has been hired to write the screenplay. Ayer tweeted an image of Harley Quinn alongside Catwoman and Poison Ivy, implying their involvement in the film. According to Mark Hughes of Forbes, production will probably start by summer 2017, with casting news early next year. Due to the film being under early stages of development, it's unclear whether the film will follow the storyline of the comics as mentioned by Mark Hughes.

I hear Margot Robbie found a writer and got DC to hire them and convinced said writer to have Harley and Ivy in a relationship not just because it's probably THE most iconic lesbian duo in comics but because Margot HATED Leto and didn't want anything to do with him after filming for SS. Seriously, he sent used condoms and dead mice to her