I need some help with this one...my sweet 2 yr old GSD and I live on a large family farm. My closest neighbors are my parents, two aunts, a cousin and her 13 year old daughter. To give you a bit of history, Gabby is a rescue and has only 3 legs. It seems the missing leg was either shot or became entangled in a tie-out and was neglected until she lost the leg completely. Long story short Gabby is a very gentle loving dog who has completed advanced training, and has her CGC. She is cautious but never aggressive to the UPS guy, Terminix man, or really any one for that matter EXCEPT my cousin's 13 year old daughter. The sight of this mild mannered girl turns Gabby into a snarling ball of terror. She lunges and growls, and bites at her completely ignoring me all the while. Part of the problem, I think is that the route to our house is through the woods, so she comes "out of nowhere" and when I'm out in the yard w/Gabby there's no need for a leash when you're surrounded by 100 acres (She tires out too quickly to run off very far). Her mother can be with her, but Gabby goes straight for the 13 year old. She has 2 dogs of her own and is fairly decent with dogs. I don't think she'd ever hurt one...she claims she wants to be a vet...but the funny thing is that my parents have a 9 year old aussie who used to have the same reaction to this girl. What is going on and how do I correct this???