Let me give the back story.
Right now I have a 9 month old German Shepherd female. In the beginning she did not have any issues with people or dogs. We went to a outdoor party with about 70 people when she was 7 months old and she was really good with people around her and loved them. There was a small white dog there who nipped her in the buttocks, and the owner ended up putting their dog away for the rest of the night in the house. Ever since that day I notice my GSD hasn't been so friendly around other people or dogs. I take her on car rides and now she barks at people who are outside. I'm inside my house and she barks at dogs/people who walk by. When she is just around people she is fine, she gets excited at first, but she calms down. When people come to my house, they can't get one foot in the door without her being right there/sometimes barking. After her first heat at 8 months, I noticed she has been becoming slightly aggressive. She won't met clean her ears with this cleaner, when I get close she grows and shows me her teeth. So I don't use it and just use my hands to clean them out (she lets me do it that way). I took her to the park to see people, animals and etc. She was great, until a dog snuck up from behind us, and her switch flipped. Her hair stood up, she barked uncontrollably and nipped me in the hand as I was pulling her away (I know she didn't mean to do it, she was trying to protect us). Also, she picks and chooses what dogs she wants to be nice to and not.
HELP HELP HELP
By the way, I have someone coming over this weekend to help me out who use to be a K9 Officer for years and he specializes in behavioral issues. He says he can work it out of her, but I am just nervous. I love my little girl
Any advice? Has this ever happened to anyone?