Aggression?

[lisyonok]

Your dog sounds like she got to her teen stage and found her confidence.
My Mischa has been a boisterous bully since she was tiny. She would never pick on dogs her size though, only on the little ones. When she got to her teen stage and became large enough to pick on the big dogs, she started bullying them too. She is only playing, but she's playing pretty rough. I personally don't let her play with small dogs, but the trainer from her day care thinks it's ok for her to play with small dogs as long as they can stand up for themselves. This is Mischa in her day care playing with a Westie called Sydney: