“Wait,” you said. “Guys, really. She can’t fly. She wouldn’t join a superteam. What’s going on?” No one knew. It just happened.

While it doesn’t relate to the flying part, there’s a funny bit in the second 52 trade where Mark Waid clears up the Bulleteer confusion:

I included Grant Morrison’s new Bulleteer as a JLAer largely as a placeholder until we could come up with a more fitting character. You can tell because she has exactly one word of dialogue and no more. Unfortunately, Grant somehow overlooked the point in the script where I asked him specifically if she was available and okay to use (PAGE THREE, YOU DRUNKEN SCOT! SEE BELOW!) and, hearing no reply, we just went with her. Grant later complained in an interview that no one had alerted him to her presence, so I’m going to send him a copy of that script page every day for the rest of his life.

At the bottom of the page, they have a script excerpt where he asks Grant if it’s cool to use Bulleteer.

Thanks, though :)