Special diet for a westie with atopic dermatitis

I am just about to adopt a 4 year old westie from a rescue centre.  She has atopic dermatitis.  I have been told by friends who have treated  dogs before that feeding them a special sensitive  diet can really help.  She has recently been very stressed because her elderly owner died and I don't know exactly what she went through but I think she had a pretty hard time of it.  She lost most of her fur but it is growing back and they say she has been responding well to treatment.  I know that skin conditions are common in westies.  She is a very  sweet natured dog and I am sure once she settles in she will start to improve even more.  Does anyone have any diet tips for me?

I would be grateful for any advice.