A behaviour i hadn't seen before

Pebbles has been taken out daily to meet other dogs on walks and to the park for the past 4 weeks. She has always been friendly to other dogs even if at times a bit too boisterous with her jumping up.
Today took her out along the streets to go to my niece's house who lives about 15 minutes walk away.
Walked past a back garden and as we were about ten feet away this huge german shepherd's head popped over the top of the back gate and he started barking at us.

Pebbles went mental!   
She started pulling and jumping up high while growling and barking in a way like never before. She seemed to be aggressive to that dog. I tried to get her to sit and give her a treat but she was so revved up she wouldn't even take the treat from me. In the end I had to pick her up and walk away.

I was not impressed with this new sudden behaviour since we have done our best to socialize her weel to both humans and other dogs.

I have a friend K, who has a female staffy and she has said that her staffy became dog aggressive practically overnight despite lots of early socialization. I was a bit doubtful about her remark but she said that when she spoke to her vet about this problem, he said to her that it was common with this breed to be dog aggressive.

  Please tell me this isn't true...

Certainly not at 15 weeks - it was more like the dog frightened her so her only reaction was to bark back at that dog.

Continue socialising her - training classes etc and I'm sure you'll be fine.

x

I hadn't thought that she may have been behaving like this out of fright.  

It does make sense when i think about it.  

It could be hard to recognise between all these doggy barks and emotions at times...She is our first  

I highly doubt that at such a young age she was acting aggressively. I agree that it was a fear response. Fight or flight, she couldn't run off so that was her only option.

Sounds to me like your little chicken got a fright and reacted to the fright by barking back, your doing a great job, keep up the good work