Dog Social Anxiety / Aggression

Hello!

My dog (2.5 year old Australian Shepherd) is struggling with what I believe is social anxiety / fear leading to aggression. Since she was a puppy, she has yelped, pulled on the leash, and become totally out of control when she sees another dog. Initially she would calm down once she got to meet the dog, so we attributed it to youthful excitement and didn’t worry too much about it. Over time, though, she has continued this behavior and started to bite some dogs (usually females) after sniffing them. After the initial meeting, if she does not bite, she is friendly and excited to play.

We recently had a baby and during my pregnancy she started reacting this same way to people on trails, and even lunging herself at the car window when we drive by pedestrians. If she meets a person she is always friendly and a bit excessively affectionate / needy, but I worry she could escalate into aggression towards humans like she has with dogs. We have taken her to a dog trainer and their techniques seemed to help in controlled environments, but did not resolve the issue.

A few more notes about her personality:
- She is extremely affectionate / needy with humans. She wants to be pet constantly and is not afraid to let you know that.
- She is generally mellow and sweet at home, other than barking when people arrive.
- For most of her life she has gotten very consistent exercise, and she was socialized consistently as a puppy, so I don’t believe those are the root causes.
- She was in a couple of minor scuffles as a puppy, but hasn’t experienced any major trauma.

Any remedy advice would be so greatly appreciated. We aren’t sure how else to help her at this point and want her to have a good quality of life. Thanks so much!