well... i know Royal Canine is a good food... it's not the highest quality you can go.. but you definitly made an improvement from the Purina! how long has she been on it?? basically if you want to feed her the BEST food.. you need one with no bi-products... something "holistic" (i was turned off it at first because of the holistic part... but it just means all natural.. no fillers)
go here
http://www.dogfoodanalysis.com/dog_f...iews/index.php
it is an AMAZING sight that gives the pros and cons to each food.. helps you sort them all out... layla's food is a 5 star.. and it is high quality.. but you can even get better stuff out there! hope this helps.