I can almost count on my thumbs the situations where I would medicate a dog other than on the advice of a vet. You might try the Benydril for a while and see if she itches less. My Vetvax catalog gives ''up to 2 mg/lb every 8 hours.'' That is the maximum dose.
How often are you bathing her and how well do you rinse? Before medicating her, you could try cutting out the baths, a good daily brushing with a soft bristled brush, and little to eat except a dog chow. Here is a link to help determine how much chow she should be getting,
http://www.puppychow.com/products/po...condition.aspx