Perhaps the two dogs have had a heirachy shift between themselves (when you were'nt there) and your GSD has perhaps dropped down a step? This perhaps would explain her being anxious and constantly harrassing the Rottie all of a sudden. It sounds like she's wanting to challenge and to 'sort this out' to regain her position, but perhaps the 'event' was so that she has no confidence in winning. A dog dropping from its position inthe pack can be very stressfull.
I used to have a bitch that was the alpha dog and as she got old, one day she was set upon by two youngsters and at that moment she dropped to the bottom of the pack. She was never the same dog again. The other dogs completely ignored her and she had towait her turn in everything. I naturally protected her and she lived on for many years without incident. But it was a sad thing to see.
I also have to agree that violence doesn't work with dogs. I can say however that on very rare occaisions you may need to be 'convincing', (not a violent angry outburst) and obedience must be obeyed immediately for the safety of you or the dog or others etc,.. But hitting out of frustration is something they simply cannot understand.
I tend to 'pinch' my dogs if they're disobedient. Just a little pinch on the bum gets their attention. :p Its closer to a nip than a slap ( or a punch...?).
