Originally Posted by Lissa
Is she getting enough physical and mental stimulation?
This is the first thing I thought too, exercise, how much exercise does your dog get? Backyard wandering doesn't count, real exercise outside of the yard. And socialization.
Dogs become possesive of their yard if they are bored.
What else does your dog have to do in its day?
Do you have a leadership role with this dog already? As in, is this your only problem area? Proper exercise and stimulation and structure often solves issues such as this.