I don't understand, she is acting like he wasn't standing right there seeing the whole thing happen? I can understand how the rest of the people weren't paying attention but you would think if some strange women approached you picking a fight. and then was interacting with your daughter, who she showed clear hostility to, would you be zoning out not paying attention to what she was doing?
Also, why lower yourself to face slapping literally? There are surely CCTV cameras in a casino, just get them to show the video and prove your daughters innocence and not lower yourself to violence like some kind of muscle brain caveman.