Wow, I have been going through skin issues with Baxter since we got him too. Pyrs being white have notoriously sensitive skin, and although I don't have problems with Sash, Bax has had big hot spots on his left hip on and off.
The rescue group had great success with Pro Plan Turkey and Barley, which we had switched him from when we first got him. He's back on it now! Several Pyr owners that we know with dogs with skin issues and even food allergies have had great success with this food, as well as the Pro Plan Salmon for sensitive skin and stomach. I know that food can be a huge debate here, and while Pro Plan is not the human-grade feed a lot of people prefer, you can't argue with this kind of success, right? And it is reasonably priced-$30 for 40 pounds, my 106 pound Pyr only needs four cups a day. :D I have found that corn is a big factor with allergy-prone dogs, too, so whatever they choose they should keep that in mind.
Also, a bit of olive oil or flaxseed oil on the food morning and evening helps too, I have done this for years with Taz and it stops the winter itchies.
For an existing hot spot, the key is to keep it dry. Gold Bond Triple Action Medicated Powder is a goldmine for this. Hot spots are self-perpetuating, ie, they are caused because the dog is so itchy he will scratch and bite and lick and that's where they come from.
My newest thing is Solid Gold Sea Meal, which Baxter has only been on for a week now. Any treatment that goes to the source of the problem does take about a month for results, so I cannot say for certain if this will help him or not, but I have seen enough before and after photos to convince me to try it. It is $19 for a pound, and you only use a teaspoon for a big dog like mine.
I hope this helps her!