You can still use the burn options of cards with a requirement she could meet when you play them, but does not meet while in play.
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Petaniqua
G4Independent: Once each combat, Petaniqua can burn 1 blood to get 1 press. She can recruit a werewolf ally as if she met the requirements of playing that card. Infernal. Red List. +1 strength.
Rulings
Her ability to get a press can only be used during the press step.
Is Independent. If the base version was the one in play, it changes sect as it is merged. If it had an anarch token, it is burned.
The ability ability cannot be used to fulfill card requirements if they are not played normally, like when using Concealed Weapon for an equipment or Piper or The Summoning for an ally.
When meeting a requirement to play a card, the vampire is treated as such for all the effects of the card, and only them, including duration effects. The vampire is not treated as meeting the requirements for effects the card has from being in play.