Hi and welcome to YT
.
So sorry to hear about your baby...the skin conditions sound miserable. The unfortunate thing about demodex/mites is that the mites can actually BURROW and live underneath the skin, causing severe ongoing problems. So, she still could very well have the mites. I'd be heading back to the vet to get a skin biopsy to see if the mites have gone under the skin.
Also, she may have a flea allergy.
If I were you with these severe of issues, I'd go to a Vet Derm asap as they will get you squared away properly, as compared to a generalist. Vet Derms are excellent!
To find one, go here:
acvd.org | Home | Veterinarians with specialized training in skin, ears, and allergy