HELLP!!! MY mouse and the vet, pleaseee!?

The vet will do a physical exam, will listen to her lungs, weigh her, and most likely will prescribe an antibiotic tail. The antibiotics are not expensive and should clear up what sounds like an upper respiratory infection. That price is very reasonable, but did you check to be sure this vet is experienced treating exotics? If the vet does not know how to dose the meds for an animal her size, insist that he or she look it up. Mice can be treated for infection. I will keep my fingers crossed for you.