I grabbed her halter, a lead line and my short whip, and we worked on personal space. And when she invaded mine I nailed her for it hard.
She's funny... she really does have an attitude, but it's easily broken through. As soon as she had the halter on she was really pretty good. I think we'll take the short bat with us when working in the paddock around her for awhile again so we're ready if she pushes it again when she's loose.
That's what I do when I'm in the pasture with the boys, especially Bob, except I use a 4ft length of 3/4" gray CPVC pipe. It's light enough, gives me plenty of reach to redirect (or smack if need be) and won't shatter. Most of the time I just walk around with it like it's a walking stick, or carry it horizontal to the ground, and they just ignore it but they definately know what it means when I raise it into "active mode" .