Australian Shepherd Question

That was a pretty dominant move on your dog's part. It isn't quite the same as aggression, but he did want to dominate her. The fact she still wanted to play says she was not scared or "offended" by his move, but recognized it as dominance. If he was being truly aggressive mostly likely she would have backed off and wanted nothing to do with him. If you had both dogs on leash, that can also create frustration and cause him to over react. It is ideal to do introductions off leash in a fenced area, though I know that is not always practical when meeting dogs while you are out walking. Another factor is once you know he may act like that you will tense up when you approach another dog, and that tension will cause him to lash out. I would suggest you work with a knowledgable behaviorist who can assess you and your dog in person, and can tailor a training program to both of you.

I had another couple thoughts. Is your dog neutered, and was the husky spayed? If not, he may be reacting to her as an intact male. Even if he is neutered, he is reaching full maturity and this is the age you may see new or stronger behaviors out of him or any dog reaching that age. It is still possible to train intact males to have manners and self control, but taking into consideration whether his behavior is hormonally motivated is something you should do.