She knew that a part of herself was in the Headmaster, fighting similarly.  At least he got to sleep through it with the Soulgament Potion, Pansy thought darkly. Unlike how a Horcrux is a piece of soul torn off and detached, used to staple one’s essence on this side of reality, the Vinculum is the consensual sharing of souls, a kind of bonding that muggles have nicknamed "twin flame’. The Headmaster would never be her soulmate, but they would feel almost as connected.