Poor her. It's hard to get them to stop isn't it? This article mentions other things besides allergies.....maybe take a look just in case? Pyoderma, atopic dermatitis, yeast infection?
https://www.vetary.com/dog/condition/itchy-skin
It mentions weather changes too, like you said. We have an Aussie who cannot run in the park grasses in the spring and fall otherwise she itches a lot. So we avoid that environment at that time of year and she is fine otherwise! I hope she gets better soon!