From that cover and her gear I'm going to say it's Barda! And the fact that she's with Steppenwolf kind a clues me to that. This is a book i will definitely be reading. I really think DC should just have an Elseworlds series that does 6 issue arcs that revolve around different worlds.
DC's problem has always been retooling, and reconning everything all the time. A retcon can be done without ignoring the complete history of the characters. A Secret origins weekly series like 52 or Birghtest day would actually be the best way to go.
Always loved Booth's art but that Young Justice TV Nightwing is AMAZING!!!! He should start rocking that in the comics the way Bppth drew that!! Nice work all around though! I've seen a lot of Medri's work, and it's all great!! He's got some very cool re-imginings.
This is only natural for him. I mean much like Magneto himself realizing the heavy handed tactics don't work, Cyclops has found a place that is between the lines, and it only makes sense that Magneto is by his side.