https://pridesource.com/article/qa-margot-robbie-talks-queen-elizabeth-drag-harley-quinns-queerness-in-birds-of-prey/ said:
In August, DC Comics confirmed that Harley Quinn and Poison Ivy are married, and in 2020, you will play Harley in her own movie. For "Birds of Prey," are you mindful of the way Harley is portrayed when it comes to her sexuality?
Robbie
Yeah. If you read the comics you know that Poison Ivy and Harley have an intimate relationship. In some comics they convey it as a friendship; in other comics you can see that they're actually sexually involved as a couple. I've been trying to – I would love to have Poison Ivy thrown into the universe, because the Harley and Poison Ivy relationship is one of my favorite aspects of the comics, so I'm looking to explore that on screen.
Have you considered who you'd want as Poison Ivy?
Robbie
You know what? I've thought about it a lot and there's no one person who springs to mind. I'm pretty open-minded.