My 7 month old GSD bites at my 7 yr old, best approach?

When my 7 yr old walks by her cage my GSD snaps and snarls at her. Today she bit her side and not in a herding way it was a dominance thing i believe. She is otherwise very well behaved and already went through obedience training. Best approach please??? Putting her in a kennel for time out doesnt seem to be working