Vampire Lady would benefit from cards that can increase its attack or decrease the attack of your opponent's monster. Most common are Equip Spell Cards, but these cards would be good on most situations.
Metalmorph increases both of monster's stats, which is good for Vampire Lady since it has balanced stats. It would be hard to surpass it even if it's switched to defense position. It can also be used to destroy high level monsters. It will gain half of the attack, of the attack target during damage calculation.
While Mirror Wall is better for defending attacks, since it reduces the attack of the attacking monster by half.
Besides from increasing the attack of a monster, Big Bang Shot gives piercing damage to a monster. Vampire Lady can inflict damage even when your opponent's monster is in defense position. Which is great since Vampire Lady's effect will activate when it inflicts battle damage.
Declares a card type / Sends from your opponent's Deck to your opponent's Graveyard
It's better to choose a Spell Card to mill from the opponent's deck because they are harder to recover.