While a face-up Level 3 or lower Normal Monster is on your side of the field, your opponent cannot select this card as an attack target. While this card is face-up on your side of the field, any Battle Damage to the controller of this card from battle involving a Level 3 or lower Normal Monster becomes 0.
There's no bug. Unhappy girl isn't a normal monster.
you know the npc deck using normal lvl 3 monsters and equipping them with that eqip spell (tribute other normal monsters on your field, gain 1000 atk for each).. yeah that's the only use of this card I can think of, but still it's crap and would only water down the deck, making it weaker..