I have read that 7-8 weeks is the earliest, but waiting until 12 weeks is recommended. I would go with what your vet said. I gave Huey's first bath at closer to 10 weeks. They can be wiped down with a damp cloth or unmedicated doggie wipes prior to that. You didn't say how old your pup is, but I think a damp washcloth with a tiny bit of mild puppy shampoo would probably feel good if she is itchy. The vet isn't recommending anything for the mites other than the one time treatment? Dawn dish soap kills fleas but I dont know about mites and I would ask the vet prior to using it on the pup. I'm sure more people with more extensive knowledge than I will respond to this question. Good luck and congrats on the new puppy. Post some photos when you can.
Oops, just saw your album. She is precious!