girls, does it always?

whenever i've seen girls smack guys, and i don't know the reasons, a lot of them will do it where they will have a hip out with a hand on it and then slap his face with her other hand. And i've NEVER seen a guy that has blocked that or ducked. Does that always work on guys? I haven't had it done to me, but if any girl tries this, what can i do to block that or duck so she misses? I wanna know, because from what i've seen, if a girl tried it right now, i'd probably get slapped, so tell me how to. I haven't seena guy that can yet.