When new photos started to come to light, one in particular got fans' attention.
One person posted a picture of Robbie in her latest Harley outfit, along with a zoomed-in picture of a tattoo on her thigh.
In the enhanced picture it's clear to see that the word 'Puddin' - Harley's nickname for her long-time lover, the Joker - has been crossed out.
This has led fans to speculate that Harley has cast off her rocking relationship with the Joker.
One person commented: "Yeah, she's rid herself of Mr. J I bet. Good detail to spot!"
Another said: "You go girl."
While a third commented: "Leto out."
Others said this could hint at Leto making a cameo in the film.
This could be linked with 'Bruce' collar charm spotted in the original selfie that Robbie posted - however no specific details of the film have been announced.
But, Warner Bros hasn't left fans in the dark all together as the company released a teaser showing Harley will not be alone in the movie - which is set to hit cinemas in February 2020.
Credit: Warner Bros.
Showing clips of Margot Robbie as Harley Quinn dancing around in an eccentric, multi-coloured coat along with brief glimpses of other characters, the trailer simply said: "See you soon."
Along with Mary Elizabeth Winstead as Huntress, Jurnee Smollett-Bell as Black Canary, Ella Jay Basco as Cassandra Cain, Rose Perez as Renee Montoya and Chris Messina as Victor Zsasz - also, did anyone else spot Ewan McGregor as Black Mask in there?
We see you, McGregor. Credit: Warner Bros
Birds of Prey will follow Harley Quinn as she teams up with other anti-heroes of DC Comics - including Black Canary, Huntress and Renee Montoya - to help a young Cassanda Cain.
While Suicide Squad didn't live up the heights of it's rivals over at Marvel, the character Harley Quinn was a huge highlight for many.
Featured Image Credit: Warner Bros.