I've seen my share of tail dockings and it's not a pretty sight. I once told the surgeon at my clinic it was like cutting off your baby's finger or something. He just laughed and admitted he didn't like doing them. That it was unnecessary. But people did it to meet breed requirements. While I understand that your case may be slightly different as this effects the health of your dog, I think you should try exercising her more first. If she is able to get some of that energy out, maybe she wouldn't be so hyper all the time, and her wagging would become less crazy. If that doesn't work and the problem continues, I would consider looking at other options. But before you do something irreversible, I would try some alternate measures first. Or even, as Nikki said, "baby" proof your house a bit. If your kid kept walking into the corner of the table and hitting their toe, you wouldn't cut it off would you? Probably not. Just a thought.