She is a sweetie!
Honestly, though, I'd get her to the vet and get it diagnosed asap before trying to treat it. Ivermectin is not a benign compound and I wouldn't want to risk it before making sure it was necessary. Even if it is
mange, you need to find out which kind of mange it is, and for that, the vet will need to do a scraping and examine any mites under the microscope.
In addition, determining dosage and treating puppies can be tricky. Best to get veterinary advice before
you start any treatment.
Depending on what she's got, there are different treatment alternatives. We had a dog that came with demodex mange (luckily, she had this type and not the contagious type because we had 5 other dogs at the time
) and we treated her with a topical. Much safer than treating her with ivermectin.