I'll follow up for Dr. B for you. There's a very good chance that your dog is seborrheic but minorly affected at this time. Which breed is she, please? Some breeds are prone to primary seborrhea - a seborrhea that doesn't develop secondary to another disease process. Here's my synopsis of seborrhea for you:
Prunary seborrhea is a hereditary disorder of keratinization. Clinical symptoms initially appear during puppyhood and may be mild at first but worsen with age. Symptoms may become apparent or worsen as an adult if underlying concurrent diseases develop.
Initially, minimal to no obvious skin changes may be seen but if the seborrhea worsens clinical signs may include a dull, dry, lusterless hair coat, excessive scaling (dandruff), follicular casts, scaly and crusty seborrheic patches and plaques, and greasy, malodorous skin. Most of the body can be involved to some degree, with interdigital areas, perineum, face, axillae, ventral neck, abdomen, and skin folds usually most severely affected. Pruritis (itchiness) can be nonexistent, mild or intense, and ceruminous otitis externa (oily external ear canal inflammation) is common. Secondary skin and ear infections with bacteria and Malassezia (yeast) are often present.
I don't know everything you've tried so I'll list a primer for treatment and prognosis for you to peruse.
1) Ensure good nutrition. A commercially balanced dog food that meets AAFCO requirements should be fed. You should find the AAFCO statement on the food label.
2) Any secondary bacterial and Malassezia skin and ear infection should be treated with appropriate topical and systemic therapies. Periodic treatments or long-term, low-dose maintenance therapy may be needed because these dogs are susceptible to recurring infection.
3) For symptomatic control of ceruminous otitis, long-term maintenance ear care is necessary. Ear treatments with a multimodal therapy (consult with her vet) or ear cleaner should be administered to both ears every 1-7 days to control cerumen (wax) accumulation.
4) For symptomatic control of seborrhea, antiseborrheic shampoos and emollients may be used every 2-7 days until the skin condition is improved (~2-3 weeks), then, bathing frequency should be decreased to every 1-2 weeks or as needed for maintenance. Antiseborrheic shampoos contain some combination of sulfur, salicyclic acid, tar, benzoyl peroxide, and phytosphingosine. Tea trea oil-containing shampoos aren't antiseborrheic and should be avoided because tea tree oil is toxic to dogs. Toxicity is most often seen in the miniature/small breeds.
5) Daily oral fatty acid supplementation may be helpful as an adjunct therapy (180mg EPA/10lbs). EPA is thought to be the most antiinflammatory of the essential omega-3 fatty acids. It's plentiful in fish oil supplements.
6) Vitamin A 8000-10,000 IU per 20lbs orally administered with a fatty meal every 24 hours. Improvement should be seen within 4-6 weeks.
7) For dogs with severe, greasy, malodorous, pruritic seborrhea, treatment with systemic corticosteroids may be helpful. Acitretin (a retinoid) may be helpful in some dogs. Calcitriol (vitamin D) may be helpful in some cases.
The prognosis is variable, depending on the severity of the seborrhea. This is an incurable condition that requires lifelong therapy for control. Please respond with further questions or concerns if you wish.