I used to own a dog grooming salon & doggy daycare many years ago. I am not a veterinarian, but I can testify that I have personally witnessed HUNDREDS of dogs miraculously reverse dozens of heartbreaking medical conditions (the majority being skin related for obvious reasons) by being fed a strict "BARF" diet - BARF = "Biologically appropriate raw food" - but even pets whose owners were too squeamish to feed it RAW enjoyed their conditions being improved dramatically with a homemade diet of mostly meat, a little bit of liver + a tiny bit of rice and vegetables.
For a little dog like yours this shouldn't be terribly expensive. I really encourage you to try it without any off-diet treats for just 8 weeks before you add more medications.
At the very least, cut out all DRY dog food because even the cheapest junk food brand of wet food is most likely going to be healthier than the abomination that is dry dog food.
I can also recommend Davis manufacturing's line of shampoo, specifically their promoxine anti itch formula. But you have to rinse well, 90% of people bathing dogs do not rinse all the soap out because they just rinse the top, like we do washing our own hair in the shower, but dogs grow hair in every single direction; imagine you are using the end of the hose/sprayer to "paint" every single square inch of her skin underneath her hair (yes, press it close) and THEN you'll have properly rinsed
(don't forget bottoms of feet too!)
Shampoo & conditioner left unrinsed is another common cause of terrible itching for dogs.
Good luck!
