[themaster]

Have there been any other instances of this "changed behaviour"?

Not sure what sort of barking it was from your post but sounds like it was an excited sort of playful barking. I'm not sure your trainers suggestion of feeding treats was going to help until you had her attention back, I think you should have just walked off in the other direction away from where she wanted to be.

If on the other hand it was aggressive braking then that should have been corrected immediately. Positive reinforcement is great but sometimes you need the correction too.