A local news reporter spoke with an extra that was on-set at Michigan State University where he claimed that have that the "character of Robin is now female".
Add to that claim that Malone was seen on set, and has been sporting a pretty serious red hair color.
It's flimsy really, but apparently this extra is now facing a $5 million dollar fine for sharing the info.
Given that Zack Snyder is obsessed with The Dark Knight Returns, an appearance by Carrie Kelly wouldn't totally be out of the cards I'd wager and Malone is a perfectly fine actress to play her (I'm a big fan), but she's also just friends with Snyder and could easily have just been visiting the set.
Could go either way really, I wouldn't run too wild with this yet.