I am sorry Nikita is losing her hair.
There are many things which can cause hairloss in dogs.
1. Skin infection (bacterial, fungal or parasite) this hair loss can be from disruption of the hair root causing hairloss or from self trauma due to the skin being itchy. Typically the skin will look abnormal (red, scaling, with broken hair shafts)
2. Hormonal disease, some hormonal disorders especially an under active thyroid gland can cause hairloss. This hairloss is often symmetrical and can affect the tail, giving the typical appearance of a rats tail. An under active thyroid gland can be diagnosed by a simple blood test.
3. Diet can cause skin disease and sometimes hairloss is seen,this is something that can really only be diagnosed once other things have been excluded and diet trials have shown improvement.
4. Specific disorders of the hair growth
cycle, these are exceedingly rare.
So if I was you I would get Nikitas thyroid levels checked and also consider specific testing of the skin (skin scrapes, hair plucks and swabs) This will identify possible infectious causes (parasites,bacteria and fungi) It may be worthwhile getting a general blood screen to ensure all her internal organs are functioning well as sometimes poor coat condition can reflect and internal disease.
In the meantime using essential fatty acids (EFAs) can help improve general skin condition which may help the hair coat, these are found in fish oils or specific veterinary skin supplements.
I hope this information helps, do message back if you have any further queries.
Good luck and I hope you get an answer soon.
Dr Dan Makin