Why does my dog get so hyped for my new neighbor

I'll preface that me and my wife rescued her 9 months ago and she is usually very stand offish even of people we have over regularly we figured she was abused (due to how skiddish she is of strangers and how we found her) but for some reason with our new neighbor she just loses her mind when she sees them she will do the whole happy dives into her and try to play with her and growled at me when I picked her up and took her away. Does anyone else that have rescued American bully's know what it is? And is there any thing I can do to fix this I liked not having to leash her when we went out since she would never leave my side