My boys get 1/2 of a scrambled egg on Sunday mornings. Jo gets oily about 2 days after a bath but Riley doesn't...if I feed them a fish based food for the higher oils Jo is a mess with very oily hair and little blisters on his belly. So, I bought a bag of Nature's Variety today...the frozen, raw food medalions...which I will start switching them over to tomorrow morning. They also make dry kibble. I talked with a lady at the store that was in line with some in her basket and she said her schnauzer had terrible itching and scratching but since she switched him to NV he's been fine and his coat is great. So, I'm going to give it a shot and see if the boys like it...I know I like the idea of a raw diet. Here's their website in case you want to look:
www.naturesvariety.com
One more thought...have you had her thyroid checked?