Hey smooth,
Let me tell you the story of my Zoe, She had demodex mites too, and she was also 6 months old.
She's all cured now, thank god, but i had a hard time with it.
Fist of all, just after it was localized they figured it out. Which pissed me off. She was on treatment for about 3 months, on ivermectin oral. I used advocate on her, and a Collar (preventic) which contains amitraz, that is great to destroy those mites. You can check it out here
The Use of Amitraz (Mitaban, Preventic Collars) in Dogs and i gave her a bath each week with dermocanis. I did all of this by my terms, the only thing the vet was giving her was ivermectin. But it's always better to ask the vet whan can you do. Now a days i use advocante, i'm always switching with advantix.
Good luck