It depends on how much itching she's doing.
If itching is so constant that skin becomes red, sore, or infected, or if hair falls out, it's too much. Just like people, they can have allergies to foods and the environment or other skin conditions. If she's not getting flea protection, it could be fleas.
Grizzly salmon oil along with vitamin e has helped my guy somewhat but he's got so many allergies that he's getting allergy shots. I've read good things about Derm caps.
You will find out a lot on this site by reading other posts.