Poor Bella. That is so upsetting! How dare they call that a nick! It is a wound , under her neck, and it must hurt her. Did the vet give her anti biotics? When my Suzi is wiggly The groomer, has anther groomer help him by having Suzi lean on the groomer , she likes the closensss of a warm body, then calms down. That is all it takes!
I hope the vet also gave your precious litte Bella pain meds too. There is no excuse for that kind of injury to ever occur at a groomer to any dog whatsoever under any circumstances.