The Wonderful Edible Egg
Exactly. Simply because she can Black Rose every turn doesn't mean she should. Being able to play conservatively and understand what you can do each turn is only a pool of choices to lead you to what you should do, you'll be all right.
In the deck, from memory, she has:
1 Cauis
2 Dandylion
3 Ryko
1 Sangan
1 Spirit Rapist
2 Debris Dragon (2k wall is huge sauce)
etc etc... That can be used in conjunction with Duality.
Not to mention using it after her Synchro spam? :v
There's a reason that Duality is so massively popular. It's not because Gold Sarcophagus is better than it.
Reread the effect on duality:
Reveal the top 3 cards of your Deck, add 1 of them to your hand, then shuffle the rest back into your Deck. You can only activate 1 "Pot of Duality" per turn.
You cannot Special Summon a monster(s) during the turn you activate this card.