Aww, your poor little girl.
Yes, these types of mites are due to immune issues...more specifically her inability to produce a certain antibody. (Actually highly believed/proven to be a hereditary condition, inherited from the dam.) Unfortunately, there is nothing that will permanently "fix" the problem or change her immune system's ability to produce the needed antibody.
However, there are a range of treaments (many mentioned here) that will keep the condition manageable. You just have to be patient--easier said than done--until you and your vet find the one that best suits her and give it time to work.
