Help! My 2 1/2 year old female lab cross has taken to growling at other little dogs - puppies and adult small dogs. This started a year ago when playing ball in the park she would be laying down catching her breath and a puppy would jump around her and mouth at her. She would tolerate it for a while and then give a snap which would usually send the puppy away.
Now when I walk her on leash, she lunges at and/or growls at small dogs. The strange thing is she is actually quite submissive most of the time - she still pees when she meets people! It's very out of character otherwise as she loves to play with other dogs. We had her through 2 rounds of puppy school from 4-8 months and she was around little dogs then and did very well. Any advice on how to cure her of this bad behaviour?