In order to gauge what would be best it would be helpful if you told us what you are currently feeding her and what you have been feeding her? What is her activity levels, your budget and what is important to you in a dog food?
I've got a two year old staffie and I feed her Orijen as I want to feed her the very best and it has to be grain free, hypoallergenic and free from any nasties while providing good value for money. At 60 pence a day, Orijen does exactly that. She is also quite an active dog so it suits her and has given her tremendous muscle definition, tone and her coat is a slick, shiny black.