I had an itchy dog, his groin area was worse than your girl's. He had raw hot spots everywhere. They're mostly gone, one or two left and not nearly as bad.
Anyway, so I went through all this. I didn't go to a dermatologist because once they know the source of the allergy the solution is custom shots for life.
Yeah you might get 'lucky' and get the results that your dog is allergic to beef and then just never give it again but it's usually more complicated. Just my opinion.
I don't know what fixed my boy. I did switch to raw in hopes to fix his allergies but it took another 6 months for them to go away so I'm not sure why they did.