Personally I wouldn't hit a female unless something drastic was going on but bitches can't just be smacking random dudes and then play like they are shocked and the victim when one doesn't give a fuck and smacks her back. Broad is lucky that big ass dude only slapped her.
Also unless dude that jumped in knew them he's a total jabroni and even then he should have been trying to shut her loud ass up prior. If that was my friend as long as dude only smacked her I would have let it be and hope she learned her lesson.