This is a trickiest part yes. Because if Shadowheart is the player character, then having her being just a puppet is concerning.
I think we can easily conclude that PC Shadowheart will be able to figure out that they are being manipulated, and decide for themselves how they want to act.
NPC Shadowheart may be helped by the protagonist, manipulated by the protagonist, or the protagonist may fail to do either successfully, resulting in the "puppet" outcome.
