LovNKyra, it's never a good idea to use Ivermectin without the supervision of a vet. Ivermectin can be toxic in dogs with a certain genetic susceptibility. The susceptibility most often but not always is found in the collie breeds. It can be fatal to dose with Ivermectin if your dog has that susceptibility.
And if your dog does not have demodex mange it's an unnecessary risk since Ivermectin will not help. In addition, we are not vets here, and we can't prescribe dosages for you.
Is there no other vet in the surrounding area that you can go to? At the very least, another scraping needs to be done. If it's still the demodex, there there will lots of mites present. (But yes, a few mites will be present on most dogs without causing disease--the mange occurs only when the immune system doesn't keep them in check.)
I strongly urge you to find another vet somewhere and get a second opinion. If there is demodex mange present, the vet you see will give you the proper dosage of ivermectin for your dog and, more importantly, be there as backup if she reacts badly to the meds.
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