I've been reading Patricia McConnell's books about animal behavior and am seeing real examples of what she describes as "controlling space"--Bonnie controls it and Darby really would like to!
This photo doesn't show it well, but one will walk ahead a bit then curve in to herd the other in the direction she wants to go.
Darby tries to do it with me a lot and she is trying to do it with Bonnie. I just keep walking forward in little tiny steps but I wish I could bend over and nip Darby on the nose like Bonnie does! Bonnie's technique seems to be a little more effective than mine!