Card Rulings:Dark Magician Girl
The effect of adding attack by 300 points, can not be negate by cards like "Divine Wrath", because the effect of increasing attack its a continues effect.
Cards like "Dark Sage", and others "Dark Magician Girl", increase the attack of this card when they are in the graveyard, because Dark Sage and Dark Magician Girl ara sub-types of Dark Magician. And you can activate cards like "Dark Magic Attack" and some else.
If there are any "Skilled Dark Magician" in any graveyard increase the attack of this card by 300. because "Skilled Dark Magician" is a "Dark Magician" monster.