Well, when I don't really wanna talk to someone, I just say "Hahaha!" It's an easy way to end a conversation... So, she probably doesn't wanna talk to you when she says that. I don't know about everyone else, but when I really wanna talk to someone, I would laugh and then say something else... So, yeah, save yourself the embarassment and when she says "hahahaha," just be like, "Okay, you keep laughing, I'm going out" Just to make her realize that just a laugh doesn't really do it...