Why she doesn't use her hand for block, for defence??

What horrible advice! Tilt the body = no CHUSHINSEN. No chushinsen = no connection, no balance, no kime, & no power. This is WKF/WUKO competition crap, not budo. Master Funakoshi said (I read somewhere) that everything one does on karate training, every block, every kick, and every punch has only one objective - doing damage to the target. And if doing damage to the target is not first and foremost on one's mind, they are not practicing Karate-Do. This is just a dance and a game of tag.