I am not an expert in this situation, I know you will get some good answers though...
When you walk through Petsmart, do you let people pet her, or do you keep to yourself and just walk through, etc... I am guessing that since this guy moved fast and had both hands out, that she felt threatened... moving towards a dog like that, and not knowing all of her background... its not an excuse for her to act that way, by any means, it just sounds like it could have been a fear thing...
The problem is, she scared the guy, by lunging at him, got the response she wanted, which was for him to back off... then returned to your side...
Hang in there, and it sounds like you have done alot with this girl, I am glad she ended up with you and not in the backyard
at her previous owners house.
Also... you may want to work on greetings, with men, probably right now with those you know... Ie: brother, relatives, etc.. and work your way up to a friendly stranger... however, let Daisy approach them, and no hands on her...let her get comfortable and then allow petting, or make her work for a treat, etc..
:D