Could Robin be a girl in Batman V Superman: Dawn of Justice?
We'll see. At present it seems unlikely, as even thoser reporting on it doubt its veracity, but apparently a script that's been making the rounds, purporting to be a Batman V Superman draft, includes Carrie Kelley will be in the film, along with fellow legacy heroes Kyle Rayner and Jason Todd.
The script in question also makes reference to Hawkman's homeworld of Thanagar (something that the Man of Steel Prequel comic book did, but not the movie itself) and Kord Industries (a regular Easter egg on Arrow and the company owned by Ted Kord, the onetime Blue Beetle).
They also mention things like a Shuster Street in Metropolis, which has a precedent in the comics, and a reference to Hobbs Bay, the district in the city colloquially referred to as "Suicide Slum."
From the report linked above, it seems (unless we are misreading) that the same script birthed both of these sets of rumors, so it's kind of an all-or-nothing. Todd's inclusion in the script makes sense given the fact that according to an earlier report, The Joker would be "mentioned when a particularly important event in Batman’s backstory is referenced," which some took to mean the death of Todd, the second Robin and later Red Hood.
Kelley, too, is somewhat logical since director Zack Snyder has made his affection for Frank Miller's The Dark Knight Returns, which introduced the character, clear.
The oddest inclusion would be Kyle Rayner, the Green Lantern of the '90s and early 2000s; while he certainly has a fan base, most are expecting either Hal Jordan to be rebooted, or John Stewart to appear in the film as Green Lantern. Nobody much has seriously considered Kyle as having Justice League potential.
Again, take this with a healthy dose of salt...but Devin Faraci at Badass Digest, who has a pretty good nose for these things, managed to poo-poo the script's odds at being the real thing while giving it enough wiggle room ("I don't want to spoil the movie a year out") to at least merit a mention.