Hi so today I was walking Luna and we always see these 2 dogs (a Yorkie and a Scottie) Luna has seen them since she was a puppy and since she has got bigger I normally keep her to heel (they are all off lead) or make her sit and wait they do sometimes come and say hi and I make Luna ignore them. Today though I let her say hi they had a quick sniff while I said hi to their owner. The Scottie was standing in front of Luna and all of a sudden was under Luna and Luna was growling (presuming Luna pinned him). I called her and she came to me her hackles were up but they go up easily when she is excited/aroused. Apart from that her body language was relaxed. Scottie dog was fine and the owner. Luna has done this before with a small bitch. Not sure if it's aggression and if it is why? Luna is 2 next month and yesterday on our walk we met different dogs little and big is fine. I understand like humans I can't expect her to like everyone but not sure what this dog did or why it happened.