maybe I take this too personal but....
its standard procedure to shave a dogs paw pads close. very close.
she could had maybe burned the paws with hot blades, you really have to make sure the blades are cool because paws are sensitive. BUT sometimes a rare dog can get irritated by clippers and its nothing that a groomer did wrong. I am not sure that what happened makes her a "lousy" groomer. the infection was more than likely caused by her chewing at her feet.
and about clipping black nails....
I dont care if you take your dog to the #1 groomer in the whole wide world, nails can still get quicked. I trim about 8 sets of nails daily, and I quick a probably a couple of dogs a week. It can happen no matter how careful you are. Black nails are a pain in the butt!
Where I live, we shave MOST of the shelties. They are usually outside dogs, not brushed, or owners say they are hot and shed too much. I mean shave the dogs... the white fur will have pink skin showing underneath it its so short. That is how they like it, and there is no way you can convince most people that is not good for a dog.
And those dogs that do come in, and the owners do not want them to have a hair cut still have to have most all of their pants shaved to the skin because of sever matting.
I promise not all groomers are the devil.