A girl that pursues men. He doesn't want to do the work in a relationship with her, he wants to keep things casual with lots of females, so he tries to line up a harem of girls to call (holla at) him. These are his holla back girls.
A girl that does wait for a guy to call her. She is impatient and insecure in the relationship, so if he gives her the slightest attention, chats her up a bit, and then tells her to call him, to "holla back" at him, she obliges happily. He forgets about her otherwise, since he is doing this with lots of girls. She does the work. She hollas back at a guy that gives her any attention at all just because he tells her to.
Jakes sees Michelle at a bar and is meeting his friends, so as he passes her he tells her to "Holla back at a brother" and keeps walking. She thinks he is interested, or else he would not have said that, so starts calling him as soon as she gets home, until she tracks him down. She is one of many girls he casually says this too, and she does whatever he wants for a date. She is a holla back girl.