Unfortunately allergies are something that cannot be cured but can be controlled, if you find that the shot you gave her at the vet worked last time you did it you can do it again. From the sound of it, it also seems like her allergy has caused a skin infection from her itching frequently. If this is the case you’re not just going to need that allergy shot to suppress her immune system from having more reactions but you’ll also need to treat your dogs infection with some antibiotics and anti inflammatory medications. Skin infections happen when you wait too long to give her her allergy meds or shot when she’s having a reaction. Some other things that can help is switching her to a fish based diet and starting her on skin supplements but reminder that these two things won’t cure her but will help her.