Dog-aggressive rescue GSD... feeling lost
I adopted a four to six year old unspayed female GSD last February. She was severely underweight, had been bred multiple times (most recently approx. 8 weeks before we adopted her), and was ditched at the high-kill Miami-Dade shelter, grabbed by a breed rescue, and allegedly temperament tested.
The aggression began to show itself after, I'd say, about two weeks. Once that happened (and we found out she had a chronic disease requiring daily meds forever, and we found out her spay was going to cost $350 - the rescue had pledged to help), I called our adoption counselor for advice, and the rescue promptly dropped off the face of the earth.
Since then, in addition to regular obedience training and manners, we have:
Tried positive reinforcement/counter-conditioning exclusively for about 3 months,
Tried "look at the dog" / "look at me" / "walk along" / BAT reactivity training for several months,
Practiced keeping her under threshold at ALL possible times (since mid February),
Used a true no-pull harness for about 9 months (to reduce the counter-pulling reflex and eliminate any negative association with other dogs from pressure on the neck),
Consulted a behaviorist,
Did blood work (no issues),
Spayed in May (at vet's advice),
Used a prong collar combined with positive reinforcement (for the past ~6 weeks)
Nothing is helping and I am desperate.
Her aggression is utterly random. One day, she will see a particular dog and positive reinforcement/chicken scraps will work and I'll be elated. The next day, or even later the same day, she can see the same dog and I will attempt the same reaction and she will fly off the handle: snarling, growling, whiny-sounding growly bark, lunging.
There is only one dog she gets along with to my knowledge, and it's my father's dog (neutered male), which gets along with every other dog he's ever seen.
She is totally just GONE when stuff like that happens. Like, on one occasion I was trying to edge her through the door when she saw another dog behind us and my keys (not an insubstantial keychain, either, I have more keys than most people I'd say) fell onto her head and she didn't even notice.
I love her so much. She is a WONDERFUL dog indoors and totally respects our cat. I mean, she obeys every rule in the house. I leave treat boxes on the floor and they are not touched. The other day actually our cat went into the milkbone box (she is very small) and our dog looked very concerned but let the cat play with the treats. If the cat wants the dog bed, she gets it and Nadya sleeps on the floor.
If it weren't for the dog-aggression, she'd be a perfect dog.
Where do I go from here? I am lost. Are there dogs that are just simply DA and who can not be rehabilitated? I will do whatever I can, and I know Nadya is smart and wants to please. It just seems like she loses her mind whenever she sees another dog, no matter what we do.