Actually, you have to take that one line (usually a card has a few more - this one is fairly straight forward) plus the damage and defense it has
4/4. She does 4 damage, so in this case she will 'fly' right through any defenders you have and do direct damage to you the player - unless you have some other card that will stop her damage. She can 'defend' with up to a 4 - say you have a card that has 3/4 (3 damage, 4 defense) and you attack me and I decide to defend with her. Your card 'dies' and she doesn't (if I remember right, she won't take any damage because she is protected from all colors <img src="/ubbthreads/images/graemlins/biggrin.gif" alt="" /> - someone who has played more recently could help on this though).
