Australian Shepherd Showing Aggression

**I posted this in working dogs, but just realized there is a forum for training and behavior so I'm posting this here too**

Hello! I have a 9 month old Aussie Puppy who is just the sweetest, most loving girl to me and almost anyone she encounters. Lately though, I've noticed her displaying signs of fear aggression. For example, at a friend's house someone walked past us in the dark backyard at night and her reaction was to lunge at him. Luckily she was on a leash, so I didn't see how that would have played out. My friend approached us and once she recognized him my puppy was happy as could be.

Another example, my friends brother was over and my puppy (her name is Reece) greeted him and was happy to see him. He went upstairs and she followed him then She returned downstairs to chew on a bone and hang out with me. When my friend's brother came back downstairs, my other little dog started barking at him suddenly for some reason and Reece (my Aussie) jumped off the couch and ran over and jumped up and nipped his arm. She put a hole in his jacket and scratched his arm with her teeth. I'm confused why she is suddenly showing these very reactive signs and trying to figure out if this is something others have dealt with?

Also, when I take her on walks and to the park she is extremely friendly to people and approaches them and licks their hands. She is *mostly* trained out of the jumping on people in excitement when they come over, but sometimes still exhibits that also (with the nipping and jumping up to lick their face) But as I said earlier, she is very loving and affectionate to the majority of people (adults). She does have a fear of tiny children though.

Some background, Reece was diagnosed with Laryngeal Paralysis at 4 months old. She was hospitalized for 3 days due to a bad stress reaction after seeing a vet she didn't like and shortly after her diagnosis. Her Laryngeal Paralysis means she can't run and play as much as other dogs because she isn't able to breathe enough when she gets too excited. She also was bit in the mouth by my friend's dog at 5 months so has had a traumatic puppyhood.

In all honesty, the stress and constant worry I have for her is eating me up. I love her to death, but right now I can't see the light at the end of the tunnel and just keep seeming to find more and more behavioral issues with her and becoming more overwhelmed and anxious.

I've started to see a behavioral trainer with her, but want to hear advice/thoughts from others as well, especially if you have experience with high energy herding dogs and aggression! Thank you!

Aussies are naturally alert dogs and will display gaurs dog behavior out of instinct. The friend coming down stairs to have her attack makes me wonder about her eye sight, since she had just seen his face before. Aussies do have many eye problems in their genes, you could have her tested if you notice anymore signs. She could see objects and figures but maybe not the details (like a face).

Reward her for being nice and make sure she knows that's it's not okay to growl or bark at people inside of the house (and outside if you don't mind her not being alert with strangers). Agressive is difficult to deal with, stay persistent! I don't think her puppy experiences would cause her to be aggressive like this. I think if being bit had caused this then it would've happened a lot sooner....

Wish you the best of luck. I have an aggressive yorkie and it took time and persistence along with plenty of socialization to get her to calm down.